code: def reverse(self):
          
          for key in six.iterkeys(self._map):
              self._map[key].reverse()
          self._items.reverse()
          return self
docs: Reverse the order of all items in the dictionary.
  
          Example:
            omd = omdict([(1,1), (1,11), (1,111), (2,2), (3,3)])
            omd.reverse()
            omd.allitems() == [(3,3), (2,2), (1,111), (1,11), (1,1)]
  
          Returns: <self>.