    def load_state_dict(self, state_dict, optimizer_overrides=None):
        """Load an LR scheduler state dict."""
        for k, state in state_dict.items():
            if k not in self.optimizers:
                # skip extra keys like "loss_scale" added by fp16 optimizer
                continue

            overrides = (
                optimizer_overrides[k]
                if isinstance(optimizer_overrides, dict) and k in optimizer_overrides
                else None
            )
            self.optimizers[k].load_state_dict(state, optimizer_overrides=overrides)
Load an LR scheduler state dict.
fairseq/optim/composite.py