code: def on_batch_end(self, last_target, train, **kwargs):
          "Update the metrics if not `train`"
          if train: return
          bs = last_target.size(0)
          for name in self.names:
              self.metrics[name] += bs * self.learn.loss_func.metrics[name].detach().cpu()
          self.nums += bf on_batch_end(self, last_target, train, **kwargs):
          "Update the metrics if not `train`"
          if train: return
          bs = last_target.size(0)
          for name in self.names:
              self.metrics[name] += bs * self.learn.loss_func.metrics[name].detach().cpu()
          self.nums += bs
docs: Update the metrics if not `train`