code: def on_validation_epoch_end(self):
      # calculate and log top1 accuracy
      if self.validation_step_outputs:
          total_num = 0
          total_correct = 0
          for num, correct in self.validation_step_outputs:
              total_num += num
              total_correct += correct
          acc = total_correct / total_num
          self.log("val_acc", acc, on_epoch=True, prog_bar=True)
          self.validation_step_outputs.clear()
  
imports: import copy
  import pytorch_lightning
  import torch
  import torch.nn
  import torchvision
  from lightly.data import LightlyDataset
  from lightly.loss import NTXentLoss
  from lightly.models import ResNetGenerator
  from lightly.models.modules.heads import MoCoProjectionHead
  from lightly.models.utils import batch_shuffle, batch_unshuffle, deactivate_requires_grad, update_momentum
  from lightly.transforms import MoCoV2Transform, utils
label_desc: Use image node_id 7 for calling the Classifier obj's underlying member method code with example usage: obj.on_validation_epoch_end() without return types