def process_decode_out(
      self, input_obj: base_input.BaseInput,
      decode_out: NestedMap) -> Tuple[NestedMap, Sequence[Tuple[str, Any]]]:
    """Processes one batch of decoded outputs.

    Args:
      input_obj: The input object where a tokenizer is accessible.
      decode_out: The output from decode(). May have an extra leading axis.

    Returns:
      - metrics, a NestedMap containing str keys and (metric, weight) pairs for
        the current batch (a tuple of two scalars).
      - A list of tuples where each element corresponds to a row in the batch.
        Each tuple is a key value pair.
    """
    raise NotImplementedError('Abstract method')