code: def from_json(cls, json):
      
      result = super(_ReducerReader, cls).from_json(json)
      result.current_key = _ReducerReader.decode_data(json["current_key"])
      result.current_values = _ReducerReader.decode_data(json["current_values"])
      return result
docs: Creates an instance of the InputReader for the given input shard state.
  
      Args:
        json: The InputReader state as a dict-like object.
  
      Returns:
        An instance of the InputReader configured using the values of json.