    def prepend_tgt_lang_tag(self) -> bool:
        """Prepend target lang ID token as the target BOS (e.g. for to-many
        multilingual setting). During inference, this requires `--prefix-size 1`
        to force BOS to be lang ID token."""
        return self.config.get("prepend_tgt_lang_tag", False)
Prepend target lang ID token as the target BOS (e.g. for to-many
multilingual setting). During inference, this requires `--prefix-size 1`
to force BOS to be lang ID token.
fairseq/data/audio/data_cfg.py