code: def filterkeys(predicate, dict_):
      
      predicate = bool if predicate is None else ensure_callable(predicate)
      ensure_mapping(dict_)
      return dict_.__class__((k, v) for k, v in iteritems(dict_) if predicate(k))
docs: Return a new dictionary comprising of keys
      for which ``predicate`` returns True, and their corresponding values.
  
      :param predicate: Predicate taking a dictionary key, or None