src/transformers/models/luke/tokenization_luke.py/LukeTokenizer/save_vocabulary
class LukeTokenizer:    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
        vocab_file, merge_file = super().save_vocabulary(save_directory, filename_prefix)

        entity_vocab_file = os.path.join(
            save_directory, (filename_prefix + "-" if filename_prefix else "") + VOCAB_FILES_NAMES["entity_vocab_file"]
        )

        with open(entity_vocab_file, "w", encoding="utf-8") as f:
            f.write(json.dumps(self.entity_vocab, ensure_ascii=False))

        return vocab_file, merge_file, entity_vocab_file