def set_src_lang_special_tokens(self, src_lang) -> None:
        """Reset the special tokens to the source lang setting.
        Prefix=[src_lang_code], suffix = [eos]
        """
        self.cur_lang_code = self.convert_tokens_to_ids(src_lang)

        if self.cur_lang_code == self.unk_token_id:
            logger.warning_once(
                f"`tgt_lang={src_lang}` has not be found in the `vocabulary`. Behaviour will probably be unexpected because the language token id will be replaced by the unknown token id."
            )

        self.init_kwargs["src_lang"] = src_lang

        self.prefix_tokens = [self.cur_lang_code]
        self.suffix_tokens = [self.eos_token_id]

        prefix_tokens_str = self.convert_ids_to_tokens(self.prefix_tokens)
        suffix_tokens_str = self.convert_ids_to_tokens(self.suffix_tokens)

        self._tokenizer.post_processor = processors.TemplateProcessing(
            single=prefix_tokens_str + ["$A"] + suffix_tokens_str,
            pair=prefix_tokens_str + ["$A", "$B"] + suffix_tokens_str,
            special_tokens=list(zip(prefix_tokens_str + suffix_tokens_str, self.prefix_tokens + self.suffix_tokens)),
        )
Reset the special tokens to the source lang setting.
        Prefix=[src_lang_code], suffix = [eos]
        
dpkd/transformers/src/transformers/models/seamless_m4t/tokenization_seamless_m4t_fast.py