def eos_token(self):
        """ End of sentence token (string). Log an error if used while not having been set. """
        if self._eos_token is None:
            logger.error("Using eos_token, but it is not set yet.")
        return self._eos_token
 End of sentence token (string). Log an error if used while not having been set. 
xtune/src/transformers/tokenization_utils.py