code: def on_after_backward(self):
      self.student_head.cancel_last_layer_gradients(
          current_epoch=self.current_epoch
      )
  
file_path: lightly/examples/pytorch_lightning/dino.py
imports: import copy
  import pytorch_lightning
  import torch
  import torchvision
  from torch import nn
  from lightly.loss import DINOLoss
  from lightly.models.modules import DINOProjectionHead
  from lightly.models.utils import deactivate_requires_grad, update_momentum
  from lightly.transforms.dino_transform import DINOTransform
  from lightly.utils.scheduler import cosine_schedule
label_desc: Use image node_id 5 for calling the DINO obj's underlying member method code with example usage: obj.on_after_backward() without return types