code: def _get_update_fn(strategy):
      
      if strategy is None:
          strategy = MS_DICTS
      try:
          return _MERGE_FNS[strategy]
      except KeyError:
          if callable(strategy):
              return strategy
  
          raise ValueError("Wrong merge strategy: %r" % strategy)
docs: Select dict-like class based on merge strategy and orderness of keys.
  
      :param merge: Specify strategy from MERGE_STRATEGIES of how to merge dicts.
      :return: Callable to update objects