def update_key_value(
        self, batch_size: int, *args, **kwargs
    ) -> Dict[str, torch.Tensor]:
        """
        Calculate metric and update average metric

        Args:
            batch_size: current batch size for metric statistics aggregation
            *args: args for metric_fn
            **kwargs: kwargs for metric_fn

        Returns:
            Dict with one element-custom metric
        """
        value = self.update(batch_size, *args, **kwargs)
        return {f"{self.metric_name}": value}

        Calculate metric and update average metric

        Args:
            batch_size: current batch size for metric statistics aggregation
            *args: args for metric_fn
            **kwargs: kwargs for metric_fn

        Returns:
            Dict with one element-custom metric
        
catalyst/metrics/_functional_metric.py