Give UserDict new __contains__ and __iter__ methods.
diff --git a/Lib/UserDict.py b/Lib/UserDict.py
index b642db7..bbd4ca0 100644
--- a/Lib/UserDict.py
+++ b/Lib/UserDict.py
@@ -40,3 +40,7 @@
         return self.data[key]
     def popitem(self):
         return self.data.popitem()
+    def __contains__(self, key):
+        return key in self.data
+    def __iter__(self):
+        return iter(self.data)