def set_src_lang_special_tokens(self, src_lang) -> None:
        """Reset the special tokens to the source lang setting.
        - In legacy mode: No prefix and suffix=[eos, src_lang_code].
        - In default mode: Prefix=[src_lang_code], suffix = [eos]
        """
        self.cur_lang_code = self.lang_code_to_id[src_lang]
        if self.legacy_behaviour:
            self.prefix_tokens = []
            self.suffix_tokens = [self.eos_token_id, self.cur_lang_code]
        else:
            self.prefix_tokens = [self.cur_lang_code]
            self.suffix_tokens = [self.eos_token_id]
Reset the special tokens to the source lang setting.
        - In legacy mode: No prefix and suffix=[eos, src_lang_code].
        - In default mode: Prefix=[src_lang_code], suffix = [eos]
        
dpkd/transformers/src/transformers/models/nllb/tokenization_nllb.py