    def __call__(self, tokens):
        """
        Maps the input tokens into indices. Its function is the same as the
        :meth:`to_indices` method.

        See detail at `to_indices`.
        """
        return self[tokens]
Maps the input tokens into indices. Its function is the same as the
:meth:`to_indices` method.

See detail at `to_indices`.
ptstructure/vqa/pytorchnlp/data/vocab.py