examples/flax/language-modeling/t5_tokenizer_model.py/SentencePieceUnigramTokenizer/add_unk_id
class SentencePieceUnigramTokenizer:    def add_unk_id(self):
        tokenizer_json = json.loads(self._tokenizer.to_str())

        tokenizer_json["model"]["unk_id"] = self.special_tokens["unk"]["id"]

        self._tokenizer = Tokenizer.from_str(json.dumps(tokenizer_json))