    def string(
        self,
        tensor,
        bpe_symbol=None,
        escape_unk=False,
        extra_symbols_to_ignore=None,
        unk_string=None,
        include_eos=False,
        separator=" ",
    ):
        """Helper for converting a tensor of token indices to a string.

        Can optionally remove BPE symbols or escape <unk> words.
        """
        if torch.is_tensor(tensor) and tensor.dim() == 2:
            return "\n".join(
                self.string(
                    t,
                    bpe_symbol,
                    escape_unk,
                    extra_symbols_to_ignore,
                    include_eos=include_eos,
                )
                for t in tensor
            )

        extra_symbols_to_ignore = set(extra_symbols_to_ignore or [])
        if not include_eos:
            extra_symbols_to_ignore.add(self.eos())

        def token_string(i):
            if i == self.unk():
                if unk_string is not None:
                    return unk_string
                else:
                    return self.unk_string(escape_unk)
            else:
                return self[i]

        if hasattr(self, "bos_index"):
            extra_symbols_to_ignore.add(self.bos())

        sent = separator.join(
            token_string(i)
            for i in tensor
            if utils.item(i) not in extra_symbols_to_ignore
        )

        return data_utils.post_process(sent, bpe_symbol)
Helper for converting a tensor of token indices to a string.

Can optionally remove BPE symbols or escape <unk> words.
fairseq/data/dictionary.py