src/transformers/models/marian/convert_marian_to_pytorch.py/OpusState/extra_keys
class OpusState:    def extra_keys(self):
        extra = []
        for k in self.state_keys:
            if (
                k.startswith("encoder_l")
                or k.startswith("decoder_l")
                or k in [CONFIG_KEY, "Wemb", "encoder_Wemb", "decoder_Wemb", "Wpos", "decoder_ff_logit_out_b"]
            ):
                continue
            else:
                extra.append(k)
        return extra