def from_json(cls, json):
    """Create new DatastoreInputReader from the json, encoded by to_json.

    Args:
      json: json map representation of DatastoreInputReader.

    Returns:
      an instance of DatastoreInputReader with all data deserialized from json.
    """
    query_range = cls(json[cls.ENTITY_KIND_PARAM],
                      key_range.KeyRange.from_json(json[cls.KEY_RANGE_PARAM]),
                      json[cls.MAPPER_PARAMS])
    return query_range
Create new DatastoreInputReader from the json, encoded by to_json.

    Args:
      json: json map representation of DatastoreInputReader.

    Returns:
      an instance of DatastoreInputReader with all data deserialized from json.
    
mapreduce/input_readers.py