def _update_lr_and_momentum_in_metrics_dict(
        self,
        metrics_dict: dict,
        lr_list: List[float],
        momentum_list: List[Union[float, None]],
    ):
        """Update learning rate and momentum in metrics_dict
        (consider only 0-th param group)

        Args:
            metrics_dict: batch_metrics or epoch_metrics
            lr_list: lr for each param group
            momentum_list: momentum for each param group

        """
        lr = lr_list[0]
        momentum = momentum_list[0]

        lr_key = f"lr/{self.scheduler_key}" if self.scheduler_key is not None else "lr"
        metrics_dict[lr_key] = lr

        if momentum is not None:
            momentum_key = (
                f"momentum/{self.scheduler_key}"
                if self.scheduler_key is not None
                else "momentum"
            )
            metrics_dict[momentum_key] = momentum
Update learning rate and momentum in metrics_dict
        (consider only 0-th param group)

        Args:
            metrics_dict: batch_metrics or epoch_metrics
            lr_list: lr for each param group
            momentum_list: momentum for each param group

        
catalyst/callbacks/scheduler.py