def cls_token(self) -> str:
        """
        `str`: Classification token, to extract a summary of an input sequence leveraging self-attention along the full
        depth of the model. Log an error if used while not having been set.
        """
        if self._cls_token is None:
            if self.verbose:
                logger.error("Using cls_token, but it is not set yet.")
            return None
        return str(self._cls_token)

        `str`: Classification token, to extract a summary of an input sequence leveraging self-attention along the full
        depth of the model. Log an error if used while not having been set.
        
dpkd/transformers/src/transformers/tokenization_utils_base.py