Converts a sequence of subtoken ids to a native string.

    Args:
      ids: a list of integers in the range [0, vocab_size)
      strip_extraneous: bool, whether to strip off extraneous tokens
        (EOS and PAD).

    Returns:
      a native string

def decode(self, ids, strip_extraneous=False):
    """Converts a sequence of subtoken ids to a native string.

    Args:
      ids: a list of integers in the range [0, vocab_size)
      strip_extraneous: bool, whether to strip off extraneous tokens
        (EOS and PAD).

    Returns:
      a native string
    """
    if strip_extraneous:
      ids = strip_ids(ids, list(range(self._num_reserved_ids or 0)))
    return unicode_to_native(
        tokenizer.decode(self._subtoken_ids_to_tokens(ids)))