Fix for Inconsistent equality and hashing

src/xmmutablemap/_core.py

@@ -89,6 +89,20 @@ def __len__(self) -> int:
         """
         return len(self._data)
 
+    def __eq__(self, other: object) -> bool:
+        """Return whether two mappings contain the same items."""
+        if isinstance(other, ImmutableMap):
+            return self._data == other._data
+        if isinstance(other, dict):
+            return self._data = other
+        if isinstance(other, Mapping):
+            return self._data == dict(other.items())
+        return NotImplemented
+
+    def __hash__(self) -> int:
+        """Return an order-insensitive hash based on the mapping contents."""
+        return hash(frozenset(self._data.items()))
+
     # ===========================================
     # Mapping Protocol