Issue #22609: Constructor of collections.UserDict now accepts the self keyword

argument.

Lib/collections/__init__.py

@@ -883,7 +883,22 @@ class ChainMap(MutableMapping):
 class UserDict(MutableMapping):
 
     # Start by filling-out the abstract methods
-    def __init__(self, dict=None, **kwargs):
+    def __init__(*args, **kwargs):
+        if not args:
+            raise TypeError("descriptor '__init__' of 'UserDict' object "
+                            "needs an argument")
+        self, *args = args
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
+        if args:
+            dict = args[0]
+        elif 'dict' in kwargs:
+            dict = kwargs.pop('dict')
+            import warnings
+            warnings.warn("Passing 'dict' as keyword argument is deprecated",
+                          PendingDeprecationWarning, stacklevel=2)
+        else:
+            dict = None
         self.data = {}
         if dict is not None:
             self.update(dict)