def is_unknown(input, model_file=None, model_proto=None, name=None):
  """Returns true if input id is unknown 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.
  """

  return _gen_sentencepiece_processor_op.sentencepiece_get_piece_type(
      input, model_file=model_file, model_proto=model_proto, name=name,
      piece_type=0)
Returns true if input id is unknown 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.