def _convert_id_to_token(self, index):
        """Converts an index (integer) in a token (str) using the vocab."""
        if self.subword_tokenizer_type == "sentencepiece":
            return self.subword_tokenizer.sp_model.IdToPiece(index)
        return self.ids_to_tokens.get(index, self.unk_token)
Converts an index (integer) in a token (str) using the vocab.
dpkd/transformers/src/transformers/models/bert_japanese/tokenization_bert_japanese.py