code: def _get_encoder_data_shapes(self, bucket_key: int, batch_size: int) -> List[mx.io.DataDesc]:
          
          return [mx.io.DataDesc(name=C.SOURCE_NAME,
                                 shape=(batch_size, bucket_key, self.num_source_factors),
                                 layout=C.BATCH_MAJOR)]
docs: Returns data shapes of the encoder module.
  
          :param bucket_key: Maximum input length.
          :return: List of data descriptions.