OrderedDict import is no longer needed (#4890)

Author: rhettinger

Lib/argparse.py

@@ -83,7 +83,6 @@
 ]
 
 
-import collections as _collections
 import os as _os
 import re as _re
 import sys as _sys
@@ -1084,7 +1083,7 @@ def __init__(self,
 
         self._prog_prefix = prog
         self._parser_class = parser_class
-        self._name_parser_map = _collections.OrderedDict()
+        self._name_parser_map = {}
         self._choices_actions = []
 
         super(_SubParsersAction, self).__init__(