def _convert_id_to_token(self, index: int) -> str:
        """Converts an index (integer) to a token (str) using the vocab."""
        if index < self.offset:
            return self.sp_model.IdToPiece(index)
        token = self.sp_model.IdToPiece(index - self.offset)
        return token
Converts an index (integer) to a token (str) using the vocab.
dpkd/transformers/src/transformers/models/pegasus/tokenization_pegasus.py