def tokens(self, batch_index: int = 0) -> List[str]:
        """
        Return the list of tokens (sub-parts of the input strings after word/subword splitting and before conversion to
        integer indices) at a given batch index (only works for the output of a fast tokenizer).

        Args:
            batch_index (`int`, *optional*, defaults to 0): The index to access in the batch.

        Returns:
            `List[str]`: The list of tokens at that index.
        """
        if not self._encodings:
            raise ValueError(
                "tokens() is not available when using non-fast tokenizers (e.g. instance of a `XxxTokenizerFast`"
                " class)."
            )
        return self._encodings[batch_index].tokens

        Return the list of tokens (sub-parts of the input strings after word/subword splitting and before conversion to
        integer indices) at a given batch index (only works for the output of a fast tokenizer).

        Args:
            batch_index (`int`, *optional*, defaults to 0): The index to access in the batch.

        Returns:
            `List[str]`: The list of tokens at that index.
        
dpkd/transformers/src/transformers/tokenization_utils_base.py