Add __contains__ method to KVStore (#1454)

* Add __contains__ method to KVStore

* Update release notes

Author: cgohlke

docs/release.rst

@@ -13,10 +13,15 @@ Release notes
     # to document your changes. On releases it will be
     # re-indented so that it does not show up in the notes.
 
-    .. _unreleased:
+.. _unreleased:
 
-    Unreleased
-    ----------
+Unreleased
+----------
+
+Bug fixes
+~~~~~~~~~
+
+* Add ``__contains__`` method to ``KVStore``. By :user:`Christoph Gohlke <cgohlke>` :issue:`1454`.
 
 .. _release_2.15.0:
 

zarr/storage.py

@@ -744,6 +744,9 @@ def __setitem__(self, key, value):
     def __delitem__(self, key):
         del self._mutable_mapping[key]
 
+    def __contains__(self, key):
+        return key in self._mutable_mapping
+
     def get(self, key, default=None):
         return self._mutable_mapping.get(key, default)