    def prepend_bos_and_append_tgt_lang_tag(self) -> bool:
        """Prepend BOS and append target lang ID token to the target (e.g. mBART with language token pretraining)."""
        return self.config.get("prepend_bos_and_append_tgt_lang_tag", False)
Prepend BOS and append target lang ID token to the target (e.g. mBART with language token pretraining).
fairseq/data/audio/data_cfg.py