code: def _register_hook(self):
      if not exists(self.layer):
          assert hasattr(
              self.vit, self.layer_name
          ), "layer whose output to take as embedding not found in vision transformer"
          layer = getattr(self.vit, self.layer_name)
      else:
          layer = self.layer
  
      handle = layer.register_forward_hook(self._hook)
      self.hooks.append(handle)
      self.hook_registered = True
  
file_path: vit-pytorch/vit_pytorch/extractor.py
imports: import torch
  from torch import nn
label_desc: Use image node_id 3 for calling the Extractor obj's underlying member method code with example usage: obj._register_hook() without return types