code: def is_unused(input, model_file=None, model_proto=None, name=None):
    
  
    return _gen_sentencepiece_processor_op.sentencepiece_get_piece_type(
        input, model_file=model_file, model_proto=model_proto, name=name,
        piece_type=2)
docs: Returns true if input id is unused piece.
  
    Args:
      input: An arbitrary tensor of int32.
      model_file: The sentencepiece model file path.
      model_proto: The sentencepiece model serialized proto.
                   Either `model_file` or `model_proto` must be set.
      name: The name argument that is passed to the op function.
    Returns:
      A tensor of bool with the same shape as input.