def on_loader_start(self, runner: "IRunner") -> None:
        """On loader star action:
        reset metric values in case of ICallbackLoaderMetric metric

        Args:
            runner: current runner
        """
        self.metric.reset(
            num_batches=runner.loader_batch_len, num_samples=runner.loader_sample_len
        )
On loader star action:
        reset metric values in case of ICallbackLoaderMetric metric

        Args:
            runner: current runner
        
catalyst/callbacks/metric.py