From a89b7668ac3b6be7f0b39fdd0bb50aa72f339585 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:35:19 +0200
Subject: [PATCH 01/53] add a dict-like checker

---
 xarray/core/utils.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index a139d2ef10a..bee5646069e 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -95,6 +95,12 @@ def maybe_coerce_to_str(index, original_coords):
 
     return index
 
+def maybe_coerce_to_dict(dict_like):
+    is_dict_like = True
+    if is_dict_like:
+        return dict_like
+    else:
+        return dict(dict_like)
 
 def safe_cast_to_index(array: Any) -> pd.Index:
     """Given an array, safely cast it to a pandas.Index.

From 8912de4349d29d80fc3170f8b9431d963fdcb8a8 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:39:01 +0200
Subject: [PATCH 02/53] Update dataset.py

---
 xarray/core/dataset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 5f5c01ad4c9..b87d4ce883a 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -755,7 +755,7 @@ def __init__(
             data_vars, coords, compat="broadcast_equals"
         )
 
-        self._attrs = dict(attrs) if attrs is not None else None
+        self._attrs = maybe_coerce_to_dict(attrs) if attrs is not None else None
         self._close = None
         self._encoding = None
         self._variables = variables

From 70c39e0a58421dd4e1ec44877f3d9e396f73f618 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:40:44 +0200
Subject: [PATCH 03/53] Update merge.py

---
 xarray/core/merge.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xarray/core/merge.py b/xarray/core/merge.py
index db5b95fd415..021de44c0d6 100644
--- a/xarray/core/merge.py
+++ b/xarray/core/merge.py
@@ -520,9 +520,9 @@ def merge_attrs(variable_attrs, combine_attrs, context=None):
     elif combine_attrs == "drop":
         return {}
     elif combine_attrs == "override":
-        return dict(variable_attrs[0])
+        return variable_attrs[0]
     elif combine_attrs == "no_conflicts":
-        result = dict(variable_attrs[0])
+        result = variable_attrs[0]
         for attrs in variable_attrs[1:]:
             try:
                 result = compat_dict_union(result, attrs)
@@ -551,7 +551,7 @@ def merge_attrs(variable_attrs, combine_attrs, context=None):
             dropped_keys |= {key for key in attrs if key not in result}
         return result
     elif combine_attrs == "identical":
-        result = dict(variable_attrs[0])
+        result = variable_attrs[0]
         for attrs in variable_attrs[1:]:
             if not dict_equiv(result, attrs):
                 raise MergeError(

From 9f46ea98f34d20971ff562ab7dbb59950238d557 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:42:05 +0200
Subject: [PATCH 04/53] Update variable.py

---
 xarray/core/variable.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index f69951580c7..c03c1ca7041 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -46,6 +46,7 @@
     ensure_us_time_resolution,
     infix_dims,
     is_duck_array,
+    maybe_coerce_to_dict,
     maybe_coerce_to_str,
 )
 
@@ -862,7 +863,7 @@ def attrs(self) -> Dict[Hashable, Any]:
 
     @attrs.setter
     def attrs(self, value: Mapping[Hashable, Any]) -> None:
-        self._attrs = dict(value)
+        self._attrs = maybe_coerce_to_dict(value)
 
     @property
     def encoding(self):

From cf11be768acc7fb9fdecfbe5aae6c82c72e539cc Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:44:27 +0200
Subject: [PATCH 05/53] Update dataset.py

---
 xarray/core/dataset.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index b87d4ce883a..379f7c8da4e 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -96,6 +96,7 @@
     infix_dims,
     is_dict_like,
     is_scalar,
+    maybe_coerce_to_dict,
     maybe_wrap_array,
 )
 from .variable import (

From 4b5b51919ec323fcbffbeef85fcc71cfa992d528 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 10:45:39 +0200
Subject: [PATCH 06/53] Update utils.py

---
 xarray/core/utils.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index bee5646069e..6d688aefd31 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -95,6 +95,7 @@ def maybe_coerce_to_str(index, original_coords):
 
     return index
 
+
 def maybe_coerce_to_dict(dict_like):
     is_dict_like = True
     if is_dict_like:
@@ -102,6 +103,7 @@ def maybe_coerce_to_dict(dict_like):
     else:
         return dict(dict_like)
 
+
 def safe_cast_to_index(array: Any) -> pd.Index:
     """Given an array, safely cast it to a pandas.Index.
 

From 043e7b6c3da553427de115fdcba9efd09b517f52 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 11:21:03 +0200
Subject: [PATCH 07/53] Update utils.py

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 6d688aefd31..2446ad52b14 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -97,7 +97,7 @@ def maybe_coerce_to_str(index, original_coords):
 
 
 def maybe_coerce_to_dict(dict_like):
-    is_dict_like = True
+    is_dict_like = False
     if is_dict_like:
         return dict_like
     else:

From 1bb3327d270e0b8a18f0f7588d4c9088bf396f48 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Tue, 3 Aug 2021 15:45:09 +0200
Subject: [PATCH 08/53] Use a shallow .copy() like dict(result) did.

---
 xarray/core/merge.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xarray/core/merge.py b/xarray/core/merge.py
index 021de44c0d6..c97a17716d0 100644
--- a/xarray/core/merge.py
+++ b/xarray/core/merge.py
@@ -520,9 +520,9 @@ def merge_attrs(variable_attrs, combine_attrs, context=None):
     elif combine_attrs == "drop":
         return {}
     elif combine_attrs == "override":
-        return variable_attrs[0]
+        return variable_attrs[0].copy()
     elif combine_attrs == "no_conflicts":
-        result = variable_attrs[0]
+        result = variable_attrs[0].copy()
         for attrs in variable_attrs[1:]:
             try:
                 result = compat_dict_union(result, attrs)
@@ -551,7 +551,7 @@ def merge_attrs(variable_attrs, combine_attrs, context=None):
             dropped_keys |= {key for key in attrs if key not in result}
         return result
     elif combine_attrs == "identical":
-        result = variable_attrs[0]
+        result = variable_attrs[0].copy()
         for attrs in variable_attrs[1:]:
             if not dict_equiv(result, attrs):
                 raise MergeError(

From e4fc98965e6cf12ad25a8ec571389067378e432c Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 4 Aug 2021 22:36:14 +0200
Subject: [PATCH 09/53] use copy() instead

---
 xarray/core/dataarray.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index cb2c4d30a69..79cdd1173ab 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -580,7 +580,7 @@ def to_dataset(
             result = self._to_dataset_whole(name)
 
         if promote_attrs:
-            result.attrs = dict(self.attrs)
+            result.attrs = self.attrs.copy()
 
         return result
 

From de21491bae01fc71850d1ed37cab99fe2afc95a2 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 4 Aug 2021 23:03:55 +0200
Subject: [PATCH 10/53] Update utils.py

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 2446ad52b14..34a85ecb4a4 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -448,7 +448,7 @@ def compat_dict_union(
     union : dict
         union of the contents.
     """
-    new_dict = dict(first_dict)
+    new_dict = first_dict.copy()
     update_safety_check(first_dict, second_dict, compat)
     new_dict.update(second_dict)
     return new_dict

From 68ac983f331f62164ff302d1df79dc33c047fbf0 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 4 Aug 2021 23:43:31 +0200
Subject: [PATCH 11/53] Update utils.py

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 34a85ecb4a4..e3da69ff347 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -426,7 +426,7 @@ def compat_dict_intersection(
 
 
 def compat_dict_union(
-    first_dict: Mapping[K, V],
+    first_dict: Dict[K, V],
     second_dict: Mapping[K, V],
     compat: Callable[[V, V], bool] = equivalent,
 ) -> MutableMapping[K, V]:

From a4a1c3d8fc662bb057224cd7b89b638e41dfc64b Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Thu, 5 Aug 2021 10:30:02 +0200
Subject: [PATCH 12/53] Initialize ds attrs the same way as in Variable

---
 xarray/core/dataset.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 379f7c8da4e..4f58128bffb 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -756,7 +756,9 @@ def __init__(
             data_vars, coords, compat="broadcast_equals"
         )
 
-        self._attrs = maybe_coerce_to_dict(attrs) if attrs is not None else None
+        self._attrs = None
+        if attrs is not None:
+            self.attrs = attrs
         self._close = None
         self._encoding = None
         self._variables = variables
@@ -796,7 +798,7 @@ def attrs(self) -> Dict[Hashable, Any]:
 
     @attrs.setter
     def attrs(self, value: Mapping[Hashable, Any]) -> None:
-        self._attrs = dict(value)
+        self._attrs = maybe_coerce_to_dict(value)
 
     @property
     def encoding(self) -> Dict:

From 93510c534031fed430cc274058a7c45f9d9d71ce Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Thu, 5 Aug 2021 10:43:30 +0200
Subject: [PATCH 13/53] change typing

---
 xarray/core/dataset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 4f58128bffb..f6c34ebbd42 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -797,7 +797,7 @@ def attrs(self) -> Dict[Hashable, Any]:
         return self._attrs
 
     @attrs.setter
-    def attrs(self, value: Mapping[Hashable, Any]) -> None:
+    def attrs(self, value: Dict[Hashable, Any]) -> None:
         self._attrs = maybe_coerce_to_dict(value)
 
     @property

From 0369166c36a29ac5fab7f098fa5f6733d6314f06 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Thu, 5 Aug 2021 10:48:33 +0200
Subject: [PATCH 14/53] more typing

---
 xarray/core/dataset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index f6c34ebbd42..1caa8af769d 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -734,7 +734,7 @@ def __init__(
         # categories
         data_vars: Mapping[Hashable, Any] = None,
         coords: Mapping[Hashable, Any] = None,
-        attrs: Mapping[Hashable, Any] = None,
+        attrs: Dict[Hashable, Any] = None,
     ):
         # TODO(shoyer): expose indexes as a public argument in __init__
 

From 40891c65edf261de5d3ad62ae8c9154e6d178436 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 6 Aug 2021 15:44:31 +0200
Subject: [PATCH 15/53] Update utils.py

---
 xarray/core/utils.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index e3da69ff347..4a77387804f 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -96,12 +96,12 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-def maybe_coerce_to_dict(dict_like):
-    is_dict_like = False
-    if is_dict_like:
-        return dict_like
+def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> Dict[Hashable, Any]:
+    """Convert to dict if the object is not a valid dict-like."""
+    if isinstance(obj, MutableMapping) and hasattr(obj, "copy"):
+        return obj
     else:
-        return dict(dict_like)
+        return dict(obj)
 
 
 def safe_cast_to_index(array: Any) -> pd.Index:

From 475cb0cace814f3163d5e9b202f6e095cc7add90 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 6 Aug 2021 15:48:49 +0200
Subject: [PATCH 16/53] shallow copy here just like with the dict

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 4a77387804f..57135057575 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -99,7 +99,7 @@ def maybe_coerce_to_str(index, original_coords):
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> Dict[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
     if isinstance(obj, MutableMapping) and hasattr(obj, "copy"):
-        return obj
+        return obj.copy()
     else:
         return dict(obj)
 

From 100731bc36847af5a7501e4ea4b1868e2333e1b9 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 6 Aug 2021 15:59:02 +0200
Subject: [PATCH 17/53] Update utils.py

---
 xarray/core/utils.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 57135057575..f6f80773117 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -8,6 +8,7 @@
 import re
 import sys
 import warnings
+from copy import copy
 from enum import Enum
 from typing import (
     TYPE_CHECKING,
@@ -99,7 +100,7 @@ def maybe_coerce_to_str(index, original_coords):
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> Dict[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
     if isinstance(obj, MutableMapping) and hasattr(obj, "copy"):
-        return obj.copy()
+        return copy(obj)
     else:
         return dict(obj)
 

From 252faf4ee54b8060b50c71cce0bb8c6432b43f91 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 6 Aug 2021 16:14:54 +0200
Subject: [PATCH 18/53] Update utils.py

---
 xarray/core/utils.py | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index f6f80773117..6dc3cd8d4b1 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -8,7 +8,6 @@
 import re
 import sys
 import warnings
-from copy import copy
 from enum import Enum
 from typing import (
     TYPE_CHECKING,
@@ -99,8 +98,8 @@ def maybe_coerce_to_str(index, original_coords):
 
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> Dict[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
-    if isinstance(obj, MutableMapping) and hasattr(obj, "copy"):
-        return copy(obj)
+    if isinstance(obj, dict):
+        return obj.copy()
     else:
         return dict(obj)
 

From f8fb503efc1ec745b1c99da4d6d9123bfd9d1cb9 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 09:44:14 +0200
Subject: [PATCH 19/53] Update conventions.py

---
 xarray/conventions.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/xarray/conventions.py b/xarray/conventions.py
index c3a05e42f82..03d478c387b 100644
--- a/xarray/conventions.py
+++ b/xarray/conventions.py
@@ -1,5 +1,6 @@
 import warnings
 from collections import defaultdict
+from copy import copy
 
 import numpy as np
 import pandas as pd
@@ -95,7 +96,7 @@ def __getitem__(self, key):
 
 
 def _var_as_tuple(var):
-    return var.dims, var.data, var.attrs.copy(), var.encoding.copy()
+    return var.dims, var.data, copy(var.attrs), var.encoding.copy()
 
 
 def maybe_encode_nonstring_dtype(var, name=None):
@@ -562,7 +563,7 @@ def stackable(dim):
                     del var_attrs[attr_name]
 
     if decode_coords and "coordinates" in attributes:
-        attributes = dict(attributes)
+        attributes = copy(attributes)
         coord_names.update(attributes.pop("coordinates").split())
 
     return new_vars, attributes, coord_names
@@ -786,7 +787,7 @@ def _encode_coordinates(variables, attributes, non_dim_coord_names):
     # http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/007571.html
     global_coordinates.difference_update(written_coords)
     if global_coordinates:
-        attributes = dict(attributes)
+        attributes = copy(attributes)
         if "coordinates" in attributes:
             warnings.warn(
                 f"cannot serialize global coordinates {global_coordinates!r} because the global "

From 6021e1214e29b9ef7004d2b272d60a9c1b5d3e6f Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 09:56:38 +0200
Subject: [PATCH 20/53] Update utils.py

---
 xarray/core/utils.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 6dc3cd8d4b1..78f361d4019 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -8,6 +8,7 @@
 import re
 import sys
 import warnings
+from copy import copy
 from enum import Enum
 from typing import (
     TYPE_CHECKING,
@@ -99,7 +100,7 @@ def maybe_coerce_to_str(index, original_coords):
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> Dict[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
     if isinstance(obj, dict):
-        return obj.copy()
+        return copy(obj)
     else:
         return dict(obj)
 
@@ -426,7 +427,7 @@ def compat_dict_intersection(
 
 
 def compat_dict_union(
-    first_dict: Dict[K, V],
+    first_dict: MutableMapping[K, V],
     second_dict: Mapping[K, V],
     compat: Callable[[V, V], bool] = equivalent,
 ) -> MutableMapping[K, V]:
@@ -448,7 +449,7 @@ def compat_dict_union(
     union : dict
         union of the contents.
     """
-    new_dict = first_dict.copy()
+    new_dict = copy(first_dict)
     update_safety_check(first_dict, second_dict, compat)
     new_dict.update(second_dict)
     return new_dict

From ccae97fc7e5490e14452b3d8045fad1a0bffae8a Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 09:59:05 +0200
Subject: [PATCH 21/53] Update dataarray.py

---
 xarray/core/dataarray.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 79cdd1173ab..4cf3f1b680d 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -1,5 +1,6 @@
 import datetime
 import warnings
+from copy import copy
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -580,7 +581,7 @@ def to_dataset(
             result = self._to_dataset_whole(name)
 
         if promote_attrs:
-            result.attrs = self.attrs.copy()
+            result.attrs = copy(self.attrs)
 
         return result
 

From 9391de6fa805a699dcedbaf63eb9f64c14d9add3 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:07:56 +0200
Subject: [PATCH 22/53] Update merge.py

---
 xarray/core/merge.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/xarray/core/merge.py b/xarray/core/merge.py
index c97a17716d0..471266cdf71 100644
--- a/xarray/core/merge.py
+++ b/xarray/core/merge.py
@@ -1,3 +1,4 @@
+from copy import copy
 from typing import (
     TYPE_CHECKING,
     AbstractSet,
@@ -520,9 +521,9 @@ def merge_attrs(variable_attrs, combine_attrs, context=None):
     elif combine_attrs == "drop":
         return {}
     elif combine_attrs == "override":
-        return variable_attrs[0].copy()
+        return copy(variable_attrs[0])
     elif combine_attrs == "no_conflicts":
-        result = variable_attrs[0].copy()
+        result = copy(variable_attrs[0])
         for attrs in variable_attrs[1:]:
             try:
                 result = compat_dict_union(result, attrs)
@@ -551,7 +552,7 @@ def merge_attrs(variable_attrs, combine_attrs, context=None):
             dropped_keys |= {key for key in attrs if key not in result}
         return result
     elif combine_attrs == "identical":
-        result = variable_attrs[0].copy()
+        result = copy(variable_attrs[0])
         for attrs in variable_attrs[1:]:
             if not dict_equiv(result, attrs):
                 raise MergeError(

From bbf4916078d6dcbbaecb79ed596ee5d247c64e5c Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:14:33 +0200
Subject: [PATCH 23/53] typing

---
 xarray/core/utils.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 78f361d4019..a86bd0f002c 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -97,9 +97,9 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> Dict[Hashable, Any]:
+def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> MutableMapping[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
-    if isinstance(obj, dict):
+    if isinstance(obj, MutableMapping):
         return copy(obj)
     else:
         return dict(obj)

From 1164f3d4bb408796c631cd9401523824ccf28a24 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:20:48 +0200
Subject: [PATCH 24/53] Update dataset.py

---
 xarray/core/dataset.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 1caa8af769d..03b474e1c1d 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -701,7 +701,7 @@ class Dataset(DataWithCoords, DatasetArithmetic, Mapping):
         description:  Weather related data.
     """
 
-    _attrs: Optional[Dict[Hashable, Any]]
+    _attrs: Optional[MutableMapping[Hashable, Any]]
     _cache: Dict[str, Any]
     _coord_names: Set[Hashable]
     _dims: Dict[Hashable, int]
@@ -790,14 +790,14 @@ def variables(self) -> Mapping[Hashable, Variable]:
         return Frozen(self._variables)
 
     @property
-    def attrs(self) -> Dict[Hashable, Any]:
+    def attrs(self) -> MutableMapping[Hashable, Any]:
         """Dictionary of global attributes on this dataset"""
         if self._attrs is None:
             self._attrs = {}
         return self._attrs
 
     @attrs.setter
-    def attrs(self, value: Dict[Hashable, Any]) -> None:
+    def attrs(self, value: MutableMapping[Hashable, Any]) -> None:
         self._attrs = maybe_coerce_to_dict(value)
 
     @property

From c5a842e7ad639c7f49de99122e0b7019db49bc1e Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:22:43 +0200
Subject: [PATCH 25/53] Update dataset.py

---
 xarray/core/dataset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 03b474e1c1d..3007a122e2a 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -734,7 +734,7 @@ def __init__(
         # categories
         data_vars: Mapping[Hashable, Any] = None,
         coords: Mapping[Hashable, Any] = None,
-        attrs: Dict[Hashable, Any] = None,
+        attrs: MutableMapping[Hashable, Any] = None,
     ):
         # TODO(shoyer): expose indexes as a public argument in __init__
 

From badc69acf1b0622f810a4823374c5e909cf2e199 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:33:42 +0200
Subject: [PATCH 26/53] Update dataset.py

---
 xarray/core/dataset.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 3007a122e2a..2f675942bb7 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -1102,7 +1102,7 @@ def _replace(
         variables: Dict[Hashable, Variable] = None,
         coord_names: Set[Hashable] = None,
         dims: Dict[Any, int] = None,
-        attrs: Union[Dict[Hashable, Any], None, Default] = _default,
+        attrs: Union[MutableMapping[Hashable, Any], None, Default] = _default,
         indexes: Union[Dict[Any, Index], None, Default] = _default,
         encoding: Union[dict, None, Default] = _default,
         inplace: bool = False,
@@ -1151,7 +1151,7 @@ def _replace_with_new_dims(
         self,
         variables: Dict[Hashable, Variable],
         coord_names: set = None,
-        attrs: Union[Dict[Hashable, Any], None, Default] = _default,
+        attrs: Union[MutableMapping[Hashable, Any], None, Default] = _default,
         indexes: Union[Dict[Hashable, Index], None, Default] = _default,
         inplace: bool = False,
     ) -> "Dataset":
@@ -1166,7 +1166,7 @@ def _replace_vars_and_dims(
         variables: Dict[Hashable, Variable],
         coord_names: set = None,
         dims: Dict[Hashable, int] = None,
-        attrs: Union[Dict[Hashable, Any], None, Default] = _default,
+        attrs: Union[MutableMapping[Hashable, Any], None, Default] = _default,
         inplace: bool = False,
     ) -> "Dataset":
         """Deprecated version of _replace_with_new_dims().
@@ -6907,7 +6907,7 @@ def polyfit(
                 covariance = xr.DataArray(Vbase, dims=("cov_i", "cov_j")) * fac
                 variables[name + "polyfit_covariance"] = covariance
 
-        return Dataset(data_vars=variables, attrs=self.attrs.copy())
+        return Dataset(data_vars=variables, attrs=copy.copy(self.attrs))
 
     def pad(
         self,
@@ -7641,6 +7641,6 @@ def _wrapper(Y, *coords_, **kwargs):
         result = result.assign_coords(
             {"param": params, "cov_i": params, "cov_j": params}
         )
-        result.attrs = self.attrs.copy()
+        result.attrs = copy.copy(self.attrs)
 
         return result

From a721f4dddd25ee7ccb43079b8b001e1eaa00ecfa Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:44:09 +0200
Subject: [PATCH 27/53] Update dataarray.py

---
 xarray/core/dataarray.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 4cf3f1b680d..02a3dbb841b 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -795,7 +795,7 @@ def loc(self) -> _LocIndexer:
         return _LocIndexer(self)
 
     @property
-    def attrs(self) -> Dict[Hashable, Any]:
+    def attrs(self) -> MutableMapping[Hashable, Any]:
         """Dictionary storing arbitrary metadata with this array."""
         return self.variable.attrs
 

From 2515a8efe821fd4703d5d7526888849fcf26cd67 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:45:45 +0200
Subject: [PATCH 28/53] Update dataarray.py

---
 xarray/core/dataarray.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index 02a3dbb841b..20890366e0d 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -10,6 +10,7 @@
     Iterable,
     List,
     Mapping,
+    MutableMapping,
     Optional,
     Sequence,
     Tuple,

From 653327cdd203943da0453eb8abeaf24bfeb7fa91 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 10:50:54 +0200
Subject: [PATCH 29/53] Update dataset.py

---
 xarray/core/dataset.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 2f675942bb7..782ef7d42cd 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -734,7 +734,7 @@ def __init__(
         # categories
         data_vars: Mapping[Hashable, Any] = None,
         coords: Mapping[Hashable, Any] = None,
-        attrs: MutableMapping[Hashable, Any] = None,
+        attrs: Mapping[Hashable, Any] = None,
     ):
         # TODO(shoyer): expose indexes as a public argument in __init__
 
@@ -797,7 +797,7 @@ def attrs(self) -> MutableMapping[Hashable, Any]:
         return self._attrs
 
     @attrs.setter
-    def attrs(self, value: MutableMapping[Hashable, Any]) -> None:
+    def attrs(self, value: Mapping[Hashable, Any]) -> None:
         self._attrs = maybe_coerce_to_dict(value)
 
     @property

From 3ad419301218ed809d4990eec8507b3d363a5f76 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 11:00:06 +0200
Subject: [PATCH 30/53] Update dataset.py

---
 xarray/core/dataset.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 782ef7d42cd..a074bbd42fd 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -798,7 +798,8 @@ def attrs(self) -> MutableMapping[Hashable, Any]:
 
     @attrs.setter
     def attrs(self, value: Mapping[Hashable, Any]) -> None:
-        self._attrs = maybe_coerce_to_dict(value)
+        # Disable type checking to work around mypy bug - see mypy#4167
+        self._attrs = maybe_coerce_to_dict(value) # type: ignore[assignment]
 
     @property
     def encoding(self) -> Dict:

From a088b16d978fc5879b8101f0a94fa19ed1f6d858 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 18:09:19 +0200
Subject: [PATCH 31/53] try coercing to dict

---
 xarray/conventions.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xarray/conventions.py b/xarray/conventions.py
index 03d478c387b..21145a8858b 100644
--- a/xarray/conventions.py
+++ b/xarray/conventions.py
@@ -11,6 +11,7 @@
 from .core.common import contains_cftime_datetimes
 from .core.pycompat import is_duck_dask_array
 from .core.variable import IndexVariable, Variable, as_variable
+from .core.utils import maybe_coerce_to_dict
 
 CF_RELATED_DATA = (
     "bounds",
@@ -563,7 +564,7 @@ def stackable(dim):
                     del var_attrs[attr_name]
 
     if decode_coords and "coordinates" in attributes:
-        attributes = copy(attributes)
+        attributes = maybe_coerce_to_dict(attributes)
         coord_names.update(attributes.pop("coordinates").split())
 
     return new_vars, attributes, coord_names

From a798f8e82c9344199b1247f8451e81f9cc2436ac Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 23:35:52 +0200
Subject: [PATCH 32/53] Update dataset.py

---
 xarray/core/dataset.py | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index a074bbd42fd..e79af3add68 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -758,7 +758,7 @@ def __init__(
 
         self._attrs = None
         if attrs is not None:
-            self.attrs = attrs
+            self.attrs = attrs  # type: ignore[assignment]  # https://github.com/python/mypy/issues/3004
         self._close = None
         self._encoding = None
         self._variables = variables
@@ -798,8 +798,7 @@ def attrs(self) -> MutableMapping[Hashable, Any]:
 
     @attrs.setter
     def attrs(self, value: Mapping[Hashable, Any]) -> None:
-        # Disable type checking to work around mypy bug - see mypy#4167
-        self._attrs = maybe_coerce_to_dict(value) # type: ignore[assignment]
+        self._attrs = maybe_coerce_to_dict(value)
 
     @property
     def encoding(self) -> Dict:

From 3391ac335d3fadffb19119f53199605606974e63 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 7 Aug 2021 23:50:04 +0200
Subject: [PATCH 33/53] Update conventions.py

---
 xarray/conventions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/conventions.py b/xarray/conventions.py
index 21145a8858b..8bd25776762 100644
--- a/xarray/conventions.py
+++ b/xarray/conventions.py
@@ -10,8 +10,8 @@
 from .core import duck_array_ops, indexing
 from .core.common import contains_cftime_datetimes
 from .core.pycompat import is_duck_dask_array
-from .core.variable import IndexVariable, Variable, as_variable
 from .core.utils import maybe_coerce_to_dict
+from .core.variable import IndexVariable, Variable, as_variable
 
 CF_RELATED_DATA = (
     "bounds",

From 68459de3bdeac71abbd588c7f914185c2fe6d55c Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 14 Aug 2021 14:58:34 +0200
Subject: [PATCH 34/53] issubclass seems slightly faster

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index a86bd0f002c..e5298493388 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -99,7 +99,7 @@ def maybe_coerce_to_str(index, original_coords):
 
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> MutableMapping[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
-    if isinstance(obj, MutableMapping):
+    if issubclass(type(obj), MutableMapping):
         return copy(obj)
     else:
         return dict(obj)

From 894b6eaa6c12cacd477805f3163f7f0b8efc34f0 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sat, 14 Aug 2021 15:27:34 +0200
Subject: [PATCH 35/53] Update utils.py

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index e5298493388..cf2bd4d1074 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -99,7 +99,7 @@ def maybe_coerce_to_str(index, original_coords):
 
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> MutableMapping[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
-    if issubclass(type(obj), MutableMapping):
+    if issubclass(obj.__class__, MutableMapping):
         return copy(obj)
     else:
         return dict(obj)

From 6f5b372401751d67d595211449d65e71f53c195f Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 20 Aug 2021 07:47:34 +0200
Subject: [PATCH 36/53] Try out TypeGuard to avoid the slow isinstance check

---
 xarray/core/utils.py | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index cf2bd4d1074..791d4abd0bd 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -38,6 +38,38 @@
 V = TypeVar("V")
 T = TypeVar("T")
 
+# TODO: Remove this check once python 3.9 is not supported:
+if sys.version_info >= (3, 9):
+    from typing import TypeGuard
+
+    def _is_MutableMapping(
+        obj: Mapping[Hashable, Any]
+    ) -> TypeGuard[MutableMapping[Hashable, Any]]:
+        """Check if the object is a mutable mapping."""
+        return hasattr(obj, "__setitem__")
+
+
+else:
+    # See GH5624, this is a convoluted way to allow type-checking to use
+    # `TypeGuard` without requiring typing_extensions as a required dependency
+    #  to _run_ the code (it is required to type-check).
+    try:
+        from typing_extensions import TypeGuard
+
+        def _is_MutableMapping(
+            obj: Mapping[Hashable, Any]
+        ) -> TypeGuard[MutableMapping[Hashable, Any]]:
+            """Check if the object is a mutable mapping."""
+            return hasattr(obj, "__setitem__")
+
+    except ImportError:
+        from typing import TYPE_CHECKING, Any
+
+        if TYPE_CHECKING:
+            raise
+        else:
+            TypeGuard = Any
+
 
 def alias_message(old_name: str, new_name: str) -> str:
     return f"{old_name} has been deprecated. Use {new_name} instead."
@@ -99,8 +131,12 @@ def maybe_coerce_to_str(index, original_coords):
 
 def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> MutableMapping[Hashable, Any]:
     """Convert to dict if the object is not a valid dict-like."""
-    if issubclass(obj.__class__, MutableMapping):
-        return copy(obj)
+    # if isinstance(obj, MutableMapping):
+    if _is_MutableMapping(obj):
+        # if hasattr(obj, "update"):
+        # return obj.copy()
+        # return copy(obj)
+        return obj
     else:
         return dict(obj)
 

From e479c5c93248cd5d54d397ac9b05f866cee5ef9b Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 20 Aug 2021 07:54:57 +0200
Subject: [PATCH 37/53] Update utils.py

---
 xarray/core/utils.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 791d4abd0bd..35b5f2aa1ed 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -63,8 +63,6 @@ def _is_MutableMapping(
             return hasattr(obj, "__setitem__")
 
     except ImportError:
-        from typing import TYPE_CHECKING, Any
-
         if TYPE_CHECKING:
             raise
         else:

From 41fd3b93f2dbf6f9d361aba11e7aaac0897d934d Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Fri, 20 Aug 2021 08:08:07 +0200
Subject: [PATCH 38/53] Update utils.py

---
 xarray/core/utils.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 5c148164bdd..d06fc1e94a6 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -38,8 +38,8 @@
 V = TypeVar("V")
 T = TypeVar("T")
 
-# TODO: Remove this check once python 3.9 is not supported:
-if sys.version_info >= (3, 9):
+# TODO: Remove this check once python 3.10 is not supported:
+if sys.version_info >= (3, 10):
     from typing import TypeGuard
 
     def _is_MutableMapping(
@@ -127,7 +127,7 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-def maybe_coerce_to_dict(obj: Mapping[Hashable, Any]) -> MutableMapping[Hashable, Any]:
+def maybe_coerce_to_dict(obj: Mapping[Any, Any]) -> MutableMapping[Any, Any]:
     """Convert to dict if the object is not a valid dict-like."""
     # if isinstance(obj, MutableMapping):
     if _is_MutableMapping(obj):

From c728006117f1734dfe4defed8fa747843d3cf2fe Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 1 Sep 2021 22:45:08 +0200
Subject: [PATCH 39/53] add typing in variable

---
 xarray/core/dataset.py  |  6 +++---
 xarray/core/variable.py | 15 ++++++++++++---
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index e1416ade690..7f43a6599be 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -698,7 +698,7 @@ class Dataset(DataWithCoords, DatasetArithmetic, Mapping):
         description:  Weather related data.
     """
 
-    _attrs: Optional[MutableMapping[Hashable, Any]]
+    _attrs: Optional[MutableMapping[Any, Any]]
     _cache: Dict[str, Any]
     _coord_names: Set[Hashable]
     _dims: Dict[Hashable, int]
@@ -787,7 +787,7 @@ def variables(self) -> Mapping[Hashable, Variable]:
         return Frozen(self._variables)
 
     @property
-    def attrs(self) -> MutableMapping[Hashable, Any]:
+    def attrs(self) -> MutableMapping[Any, Any]:
         """Dictionary of global attributes on this dataset"""
         if self._attrs is None:
             self._attrs = {}
@@ -1099,7 +1099,7 @@ def _replace(
         variables: Dict[Hashable, Variable] = None,
         coord_names: Set[Hashable] = None,
         dims: Dict[Any, int] = None,
-        attrs: Union[MutableMapping[Hashable, Any], None, Default] = _default,
+        attrs: Union[MutableMapping[Any, Any], None, Default] = _default,
         indexes: Union[Dict[Any, Index], None, Default] = _default,
         encoding: Union[dict, None, Default] = _default,
         inplace: bool = False,
diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index ddda4f8b49a..34aafb045a4 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -13,6 +13,7 @@
     Hashable,
     List,
     Mapping,
+    MutableMapping,
     Optional,
     Sequence,
     Tuple,
@@ -285,10 +286,18 @@ class Variable(AbstractArray, NdimSizeLenMixin, VariableArithmetic):
     form of a Dataset or DataArray should almost always be preferred, because
     they can use more complete metadata in context of coordinate labels.
     """
+    _attrs: Optional[MutableMapping[Any, Any]]
 
     __slots__ = ("_dims", "_data", "_attrs", "_encoding")
 
-    def __init__(self, dims, data, attrs=None, encoding=None, fastpath=False):
+    def __init__(
+        self,
+        dims,
+        data,
+        attrs: Optional[Mapping[Any, Any]] = None,
+        encoding=None,
+        fastpath=False
+    ):
         """
         Parameters
         ----------
@@ -313,7 +322,7 @@ def __init__(self, dims, data, attrs=None, encoding=None, fastpath=False):
         self._attrs = None
         self._encoding = None
         if attrs is not None:
-            self.attrs = attrs
+            self.attrs = attrs  # type: ignore[assignment]  # https://github.com/python/mypy/issues/3004
         if encoding is not None:
             self.encoding = encoding
 
@@ -863,7 +872,7 @@ def __setitem__(self, key, value):
         indexable[index_tuple] = value
 
     @property
-    def attrs(self) -> Dict[Hashable, Any]:
+    def attrs(self) -> MutableMapping[Any, Any]:
         """Dictionary of local attributes on this variable."""
         if self._attrs is None:
             self._attrs = {}

From 0558996d939476a2f2c72f6fb99c948157fca4f0 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 1 Sep 2021 22:55:04 +0200
Subject: [PATCH 40/53] lint

---
 xarray/core/variable.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index 34aafb045a4..9145293ca3c 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -286,6 +286,7 @@ class Variable(AbstractArray, NdimSizeLenMixin, VariableArithmetic):
     form of a Dataset or DataArray should almost always be preferred, because
     they can use more complete metadata in context of coordinate labels.
     """
+
     _attrs: Optional[MutableMapping[Any, Any]]
 
     __slots__ = ("_dims", "_data", "_attrs", "_encoding")
@@ -296,7 +297,7 @@ def __init__(
         data,
         attrs: Optional[Mapping[Any, Any]] = None,
         encoding=None,
-        fastpath=False
+        fastpath=False,
     ):
         """
         Parameters

From 320debb55e7cec8b866dee44ac064f692241e573 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 1 Sep 2021 23:00:18 +0200
Subject: [PATCH 41/53] hashable -> any

---
 xarray/core/dataset.py | 4 ++--
 xarray/core/utils.py   | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 7f43a6599be..bcc9f9f34c8 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -1148,7 +1148,7 @@ def _replace_with_new_dims(
         self,
         variables: Dict[Hashable, Variable],
         coord_names: set = None,
-        attrs: Union[MutableMapping[Hashable, Any], None, Default] = _default,
+        attrs: Union[MutableMapping[Any, Any], None, Default] = _default,
         indexes: Union[Dict[Hashable, Index], None, Default] = _default,
         inplace: bool = False,
     ) -> "Dataset":
@@ -1163,7 +1163,7 @@ def _replace_vars_and_dims(
         variables: Dict[Hashable, Variable],
         coord_names: set = None,
         dims: Dict[Hashable, int] = None,
-        attrs: Union[MutableMapping[Hashable, Any], None, Default] = _default,
+        attrs: Union[MutableMapping[Any, Any], None, Default] = _default,
         inplace: bool = False,
     ) -> "Dataset":
         """Deprecated version of _replace_with_new_dims().
diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 4bbc88230df..441eb4eeb18 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -43,8 +43,8 @@
     from typing import TypeGuard
 
     def _is_MutableMapping(
-        obj: Mapping[Hashable, Any]
-    ) -> TypeGuard[MutableMapping[Hashable, Any]]:
+        obj: Mapping[Any, Any]
+    ) -> TypeGuard[MutableMapping[Any, Any]]:
         """Check if the object is a mutable mapping."""
         return hasattr(obj, "__setitem__")
 
@@ -57,8 +57,8 @@ def _is_MutableMapping(
         from typing_extensions import TypeGuard
 
         def _is_MutableMapping(
-            obj: Mapping[Hashable, Any]
-        ) -> TypeGuard[MutableMapping[Hashable, Any]]:
+            obj: Mapping[Any, Any]
+        ) -> TypeGuard[MutableMapping[Any, Any]]:
             """Check if the object is a mutable mapping."""
             return hasattr(obj, "__setitem__")
 

From 596c661f6d4b38a50a7dd947f689bd2c09fddc6d Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 1 Sep 2021 23:10:41 +0200
Subject: [PATCH 42/53] add typing to indexvariable

---
 xarray/core/variable.py | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index 9145293ca3c..bf33a805f99 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -2583,10 +2583,18 @@ class IndexVariable(Variable):
     They also have a name property, which is the name of their sole dimension
     unless another name is given.
     """
+    _attrs: Optional[MutableMapping[Any, Any]]
 
     __slots__ = ()
 
-    def __init__(self, dims, data, attrs=None, encoding=None, fastpath=False):
+    def __init__(
+        self,
+        dims,
+        data,
+        attrs: Optional[Mapping[Any, Any]] = None,
+        encoding=None,
+        fastpath=False,
+    ):
         super().__init__(dims, data, attrs, encoding, fastpath)
         if self.ndim != 1:
             raise ValueError(f"{type(self).__name__} objects must be 1-dimensional")

From 4e5b2620d950f1819e92933ed2410ee4ce0233b8 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 1 Sep 2021 23:13:16 +0200
Subject: [PATCH 43/53] Update variable.py

---
 xarray/core/variable.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xarray/core/variable.py b/xarray/core/variable.py
index bf33a805f99..3468d5b5884 100644
--- a/xarray/core/variable.py
+++ b/xarray/core/variable.py
@@ -2583,6 +2583,7 @@ class IndexVariable(Variable):
     They also have a name property, which is the name of their sole dimension
     unless another name is given.
     """
+
     _attrs: Optional[MutableMapping[Any, Any]]
 
     __slots__ = ()

From 84b494f5100d35c3093f4de4883639293b456790 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 31 Oct 2021 10:08:41 +0100
Subject: [PATCH 44/53] Update utils.py

---
 xarray/core/utils.py | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 1a7c1315f18..6ceb622198c 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -40,32 +40,8 @@
 # TODO: Remove this check once python 3.10 is not supported:
 if sys.version_info >= (3, 10):
     from typing import TypeGuard
-
-    def _is_MutableMapping(
-        obj: Mapping[Any, Any]
-    ) -> TypeGuard[MutableMapping[Any, Any]]:
-        """Check if the object is a mutable mapping."""
-        return hasattr(obj, "__setitem__")
-
-
 else:
-    # See GH5624, this is a convoluted way to allow type-checking to use
-    # `TypeGuard` without requiring typing_extensions as a required dependency
-    #  to _run_ the code (it is required to type-check).
-    try:
-        from typing_extensions import TypeGuard
-
-        def _is_MutableMapping(
-            obj: Mapping[Any, Any]
-        ) -> TypeGuard[MutableMapping[Any, Any]]:
-            """Check if the object is a mutable mapping."""
-            return hasattr(obj, "__setitem__")
-
-    except ImportError:
-        if TYPE_CHECKING:
-            raise
-        else:
-            TypeGuard = Any
+    from typing_extensions import TypeGuard
 
 
 def alias_message(old_name: str, new_name: str) -> str:
@@ -126,6 +102,11 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
+def _is_MutableMapping(obj: Mapping[Any, Any]) -> TypeGuard[MutableMapping[Any, Any]]:
+    """Check if the object is a mutable mapping."""
+    return hasattr(obj, "__setitem__")
+
+
 def maybe_coerce_to_dict(obj: Mapping[Any, Any]) -> MutableMapping[Any, Any]:
     """Convert to dict if the object is not a valid dict-like."""
     # if isinstance(obj, MutableMapping):

From 8c09d4a32a89e53237c4179949028d11989a9c59 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 31 Oct 2021 10:23:54 +0100
Subject: [PATCH 45/53] TypeGuard not in typing_extensions 3.7

---
 xarray/core/utils.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 6ceb622198c..33e32a4a61e 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -40,6 +40,8 @@
 # TODO: Remove this check once python 3.10 is not supported:
 if sys.version_info >= (3, 10):
     from typing import TypeGuard
+elif sys.version_info == (3, 7):
+    TypeGuard = Any
 else:
     from typing_extensions import TypeGuard
 

From 9758348ee5415f665fe47f97cd1130fe4d4e0f77 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 31 Oct 2021 10:34:06 +0100
Subject: [PATCH 46/53] Update utils.py

---
 xarray/core/utils.py | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 33e32a4a61e..ab3292ea6a6 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -37,14 +37,6 @@
 V = TypeVar("V")
 T = TypeVar("T")
 
-# TODO: Remove this check once python 3.10 is not supported:
-if sys.version_info >= (3, 10):
-    from typing import TypeGuard
-elif sys.version_info == (3, 7):
-    TypeGuard = Any
-else:
-    from typing_extensions import TypeGuard
-
 
 def alias_message(old_name: str, new_name: str) -> str:
     return f"{old_name} has been deprecated. Use {new_name} instead."
@@ -104,9 +96,31 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-def _is_MutableMapping(obj: Mapping[Any, Any]) -> TypeGuard[MutableMapping[Any, Any]]:
-    """Check if the object is a mutable mapping."""
-    return hasattr(obj, "__setitem__")
+# See GH5624, this is a convoluted way to allow type-checking to use `TypeGuard` without
+# requiring typing_extensions as a required dependency to _run_ the code (it is required
+# to type-check).
+try:
+    if sys.version_info >= (3, 10):
+        from typing import TypeGuard
+    else:
+        from typing_extensions import TypeGuard
+except ImportError:
+    if TYPE_CHECKING:
+        raise
+    else:
+
+        def _is_MutableMapping(
+            obj: Mapping[Any, Any]
+        ) -> TypeGuard[MutableMapping[Any, Any]]:
+            """Check if the object is a mutable mapping."""
+            return hasattr(obj, "__setitem__")
+
+
+else:
+
+    def _is_MutableMapping(obj: Mapping[Any, Any]) -> bool:
+        """Check if the object is a mutable mapping."""
+        return hasattr(obj, "__setitem__")
 
 
 def maybe_coerce_to_dict(obj: Mapping[Any, Any]) -> MutableMapping[Any, Any]:

From 2192835e79cdb0bcabf777092f253e2c5b3179e7 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 31 Oct 2021 10:41:11 +0100
Subject: [PATCH 47/53] Update utils.py

---
 xarray/core/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index ab3292ea6a6..65343909c14 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -104,7 +104,7 @@ def maybe_coerce_to_str(index, original_coords):
         from typing import TypeGuard
     else:
         from typing_extensions import TypeGuard
-except ImportError:
+except NameError:
     if TYPE_CHECKING:
         raise
     else:

From b995c4a3b4ba688444450c817b52f65d81a6831b Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 31 Oct 2021 10:48:39 +0100
Subject: [PATCH 48/53] Update utils.py

---
 xarray/core/utils.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 65343909c14..f453f675740 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -104,9 +104,9 @@ def maybe_coerce_to_str(index, original_coords):
         from typing import TypeGuard
     else:
         from typing_extensions import TypeGuard
-except NameError:
+except (ImportError, NameError) as e:
     if TYPE_CHECKING:
-        raise
+        raise e
     else:
 
         def _is_MutableMapping(

From 650ce2294cdfb7b999aa5e1efbf5139909e1c132 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 31 Oct 2021 10:54:10 +0100
Subject: [PATCH 49/53] Update utils.py

---
 xarray/core/utils.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index f453f675740..ad2531a525b 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -109,16 +109,16 @@ def maybe_coerce_to_str(index, original_coords):
         raise e
     else:
 
-        def _is_MutableMapping(
-            obj: Mapping[Any, Any]
-        ) -> TypeGuard[MutableMapping[Any, Any]]:
+        def _is_MutableMapping(obj: Mapping[Any, Any]) -> bool:
             """Check if the object is a mutable mapping."""
             return hasattr(obj, "__setitem__")
 
 
 else:
 
-    def _is_MutableMapping(obj: Mapping[Any, Any]) -> bool:
+    def _is_MutableMapping(
+        obj: Mapping[Any, Any]
+    ) -> TypeGuard[MutableMapping[Any, Any]]:
         """Check if the object is a mutable mapping."""
         return hasattr(obj, "__setitem__")
 

From 1f0d41bfeb7fd4412d638c39b920fb3b3ba8bfcb Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 14 Nov 2021 16:40:49 +0100
Subject: [PATCH 50/53] typing_extensions now a required package

---
 xarray/core/utils.py | 35 ++++++++++-------------------------
 1 file changed, 10 insertions(+), 25 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index ad2531a525b..cb96a006636 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -33,6 +33,11 @@
 import numpy as np
 import pandas as pd
 
+if sys.version_info >= (3, 10):
+    from typing import TypeGuard
+else:
+    from typing_extensions import TypeGuard
+
 K = TypeVar("K")
 V = TypeVar("V")
 T = TypeVar("T")
@@ -96,31 +101,11 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-# See GH5624, this is a convoluted way to allow type-checking to use `TypeGuard` without
-# requiring typing_extensions as a required dependency to _run_ the code (it is required
-# to type-check).
-try:
-    if sys.version_info >= (3, 10):
-        from typing import TypeGuard
-    else:
-        from typing_extensions import TypeGuard
-except (ImportError, NameError) as e:
-    if TYPE_CHECKING:
-        raise e
-    else:
-
-        def _is_MutableMapping(obj: Mapping[Any, Any]) -> bool:
-            """Check if the object is a mutable mapping."""
-            return hasattr(obj, "__setitem__")
-
-
-else:
-
-    def _is_MutableMapping(
-        obj: Mapping[Any, Any]
-    ) -> TypeGuard[MutableMapping[Any, Any]]:
-        """Check if the object is a mutable mapping."""
-        return hasattr(obj, "__setitem__")
+def _is_MutableMapping(
+    obj: Mapping[Any, Any]
+) -> TypeGuard[MutableMapping[Any, Any]]:
+    """Check if the object is a mutable mapping."""
+    return hasattr(obj, "__setitem__")
 
 
 def maybe_coerce_to_dict(obj: Mapping[Any, Any]) -> MutableMapping[Any, Any]:

From 3661d43945abfb14013e4245acf10a456d0a1719 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Sun, 14 Nov 2021 15:42:52 +0000
Subject: [PATCH 51/53] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 xarray/core/utils.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index cb96a006636..acb76d3003a 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -101,9 +101,7 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-def _is_MutableMapping(
-    obj: Mapping[Any, Any]
-) -> TypeGuard[MutableMapping[Any, Any]]:
+def _is_MutableMapping(obj: Mapping[Any, Any]) -> TypeGuard[MutableMapping[Any, Any]]:
     """Check if the object is a mutable mapping."""
     return hasattr(obj, "__setitem__")
 

From a494fd7e52a1f04b10beae48b5557922350986fd Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 14 Nov 2021 16:50:07 +0100
Subject: [PATCH 52/53] TypeGuard still not in typing_extensions 3.7

---
 xarray/core/utils.py | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index acb76d3003a..ad2531a525b 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -33,11 +33,6 @@
 import numpy as np
 import pandas as pd
 
-if sys.version_info >= (3, 10):
-    from typing import TypeGuard
-else:
-    from typing_extensions import TypeGuard
-
 K = TypeVar("K")
 V = TypeVar("V")
 T = TypeVar("T")
@@ -101,9 +96,31 @@ def maybe_coerce_to_str(index, original_coords):
     return index
 
 
-def _is_MutableMapping(obj: Mapping[Any, Any]) -> TypeGuard[MutableMapping[Any, Any]]:
-    """Check if the object is a mutable mapping."""
-    return hasattr(obj, "__setitem__")
+# See GH5624, this is a convoluted way to allow type-checking to use `TypeGuard` without
+# requiring typing_extensions as a required dependency to _run_ the code (it is required
+# to type-check).
+try:
+    if sys.version_info >= (3, 10):
+        from typing import TypeGuard
+    else:
+        from typing_extensions import TypeGuard
+except (ImportError, NameError) as e:
+    if TYPE_CHECKING:
+        raise e
+    else:
+
+        def _is_MutableMapping(obj: Mapping[Any, Any]) -> bool:
+            """Check if the object is a mutable mapping."""
+            return hasattr(obj, "__setitem__")
+
+
+else:
+
+    def _is_MutableMapping(
+        obj: Mapping[Any, Any]
+    ) -> TypeGuard[MutableMapping[Any, Any]]:
+        """Check if the object is a mutable mapping."""
+        return hasattr(obj, "__setitem__")
 
 
 def maybe_coerce_to_dict(obj: Mapping[Any, Any]) -> MutableMapping[Any, Any]:

From 0e6036f383614ba3795a9ad9035349c42d38c2c9 Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Sun, 14 Nov 2021 17:03:50 +0100
Subject: [PATCH 53/53] Update utils.py

---
 xarray/core/utils.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index ad2531a525b..1f66a4c6928 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -129,8 +129,8 @@ def maybe_coerce_to_dict(obj: Mapping[Any, Any]) -> MutableMapping[Any, Any]:
     if _is_MutableMapping(obj):
         # if hasattr(obj, "update"):
         # return obj.copy()
-        # return copy(obj)
-        return obj
+        return copy(obj)
+        # return obj
     else:
         return dict(obj)