code: def from_json(cls, json, _reader=blobstore.BlobReader):
      
      return cls(json[cls.BLOB_KEY_PARAM],
                 json[cls.START_FILE_INDEX_PARAM],
                 json[cls.END_FILE_INDEX_PARAM],
                 json[cls.OFFSET_PARAM],
                 _reader)
docs: Creates an instance of the InputReader for the given input shard state.
  
      Args:
        json: The InputReader state as a dict-like object.
        _reader: For dependency injection.
  
      Returns:
        An instance of the InputReader configured using the values of json.