bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113)

(cherry picked from commit e0e5065daef36dafe10a46eaa8b7800274d73062)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index 3f26380..dbed993 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -1134,10 +1134,13 @@
 
 
 DictProxy = MakeProxyType('DictProxy', (
-    '__contains__', '__delitem__', '__getitem__', '__len__',
+    '__contains__', '__delitem__', '__getitem__', '__iter__', '__len__',
     '__setitem__', 'clear', 'copy', 'get', 'has_key', 'items',
     'keys', 'pop', 'popitem', 'setdefault', 'update', 'values'
     ))
+DictProxy._method_to_typeid_ = {
+    '__iter__': 'Iterator',
+    }
 
 
 ArrayProxy = MakeProxyType('ArrayProxy', (