code: def state_shapes(self,
                       batch_size: int,
                       target_max_length: int,
                       source_encoded_max_length: int,
                       source_encoded_depth: int) -> List[mx.io.DataDesc]:
          
          pass
docs: Returns a list of shape descriptions given batch size, encoded source max length and encoded source depth.
          Used for inference.
  
          :param batch_size: Batch size during inference.
          :param target_max_length: Current target sequence length.
          :param source_encoded_max_length: Size of encoder time dimension.
          :param source_encoded_depth: Depth of encoded source.
          :return: List of shape descriptions.