diff --git a/pydtk/db/schemas/__init__.py b/pydtk/db/schemas/__init__.py
index b989efa..77524ff 100644
--- a/pydtk/db/schemas/__init__.py
+++ b/pydtk/db/schemas/__init__.py
@@ -1,4 +1,5 @@
 """Schemas."""
+
 import glob
 import importlib
 import inspect
diff --git a/pydtk/db/v1/handlers/__init__.py b/pydtk/db/v1/handlers/__init__.py
index 1dfc6f1..a008448 100644
--- a/pydtk/db/v1/handlers/__init__.py
+++ b/pydtk/db/v1/handlers/__init__.py
@@ -105,9 +105,11 @@ def _get_uuid_from_item(self, item):
         """
         pre_hash = "".join(
             [
-                "{:.09f}".format(item[c["name"]])
-                if isinstance(item[c["name"]], float)
-                else str(item[c["name"]])
+                (
+                    "{:.09f}".format(item[c["name"]])
+                    if isinstance(item[c["name"]], float)
+                    else str(item[c["name"]])
+                )
                 for c in self.columns
                 if c["name"] in item.keys()
             ]
diff --git a/pydtk/db/v2/handlers/__init__.py b/pydtk/db/v2/handlers/__init__.py
index 0cdd0d3..35cff03 100644
--- a/pydtk/db/v2/handlers/__init__.py
+++ b/pydtk/db/v2/handlers/__init__.py
@@ -159,9 +159,7 @@ def _initialize_engine(
             engine = (
                 "postgresql"
                 if engine == "timescaledb"
-                else "mysql"
-                if engine == "mariadb"
-                else engine
+                else "mysql" if engine == "mariadb" else engine
             )
             username_and_password = (
                 ""
@@ -214,9 +212,11 @@ def _get_uuid_from_item(self, data_in):
 
         pre_hash = "".join(
             [
-                "{:.09f}".format(item[c["name"]])
-                if isinstance(item[c["name"]], float)
-                else str(item[c["name"]])
+                (
+                    "{:.09f}".format(item[c["name"]])
+                    if isinstance(item[c["name"]], float)
+                    else str(item[c["name"]])
+                )
                 for c in self.columns
                 if c["name"] in item.keys()
             ]
diff --git a/pydtk/db/v3/handlers/__init__.py b/pydtk/db/v3/handlers/__init__.py
index a293b0d..a23180f 100644
--- a/pydtk/db/v3/handlers/__init__.py
+++ b/pydtk/db/v3/handlers/__init__.py
@@ -233,9 +233,11 @@ def _get_uuid_from_item(self, data_in):
 
         pre_hash = "".join(
             [
-                "{:.09f}".format(item[column])
-                if isinstance(item[column], float)
-                else str(item[column])
+                (
+                    "{:.09f}".format(item[column])
+                    if isinstance(item[column], float)
+                    else str(item[column])
+                )
                 for column in hash_target_columns
                 if column in item.keys()
             ]
diff --git a/pydtk/db/v4/handlers/__init__.py b/pydtk/db/v4/handlers/__init__.py
index 86287eb..2fa45ab 100644
--- a/pydtk/db/v4/handlers/__init__.py
+++ b/pydtk/db/v4/handlers/__init__.py
@@ -423,11 +423,15 @@ def _get_uuid_from_item(self, data_in):
 
         pre_hash = "".join(
             [
-                "{:.09f}".format(item[column])
-                if isinstance(item[column], float)
-                else str(item[column].keys())
-                if isinstance(item[column], dict)
-                else str(item[column])
+                (
+                    "{:.09f}".format(item[column])
+                    if isinstance(item[column], float)
+                    else (
+                        str(item[column].keys())
+                        if isinstance(item[column], dict)
+                        else str(item[column])
+                    )
+                )
                 for column in hash_target_columns
                 if column in item.keys()
             ]
diff --git a/pydtk/models/__init__.py b/pydtk/models/__init__.py
index fd4cc0f..b2887e1 100644
--- a/pydtk/models/__init__.py
+++ b/pydtk/models/__init__.py
@@ -133,9 +133,9 @@ def to_dict(self):
             elif isinstance(value, dict):
                 result[attr] = dict(
                     map(
-                        lambda item: (item[0], item[1].to_dict())
-                        if hasattr(item[1], "to_dict")
-                        else item,
+                        lambda item: (
+                            (item[0], item[1].to_dict()) if hasattr(item[1], "to_dict") else item
+                        ),
                         value.items(),
                     )
                 )
@@ -527,9 +527,9 @@ def to_dict(self):
             elif isinstance(value, dict):
                 result[attr] = dict(
                     map(
-                        lambda item: (item[0], item[1].to_dict())
-                        if hasattr(item[1], "to_dict")
-                        else item,
+                        lambda item: (
+                            (item[0], item[1].to_dict()) if hasattr(item[1], "to_dict") else item
+                        ),
                         value.items(),
                     )
                 )
diff --git a/pydtk/utils/imports.py b/pydtk/utils/imports.py
index 0b9aeaa..b3c498f 100644
--- a/pydtk/utils/imports.py
+++ b/pydtk/utils/imports.py
@@ -1,6 +1,5 @@
 """Import utilities."""
 
-
 import importlib
 import importlib.util