code: def test_add_remove_ddp_hooks(self) -> None:
      remaining_hooks = {
          "attached": None,
          "detached": None,
      }
  
      run_function(
          add_remove_ddp_hooks,
          remaining_hooks,
          dp=True,
          noise_multiplier=0.1,
          max_grad_norm=1.0,
      )
  
      assert remaining_hooks["attached"], "There are no hooks."
  
      assert not remaining_hooks[
          "detached"
      ], f"Some hooks remain after .remove_hooks(): {remaining_hooks}"
  
imports: import os
  import sys
  import unittest
  import torch
  import torch.distributed
  import torch.multiprocessing
  import torch.nn
  import torch.optim
  from opacus import PrivacyEngine
  from opacus.distributed import DifferentiallyPrivateDistributedDataParallel
  from torch.nn.parallel import DistributedDataParallel
label_desc: Use image node_id 4 for calling the GradientComputationTest obj's underlying member method code with example usage: obj.test_add_remove_ddp_hooks() without return types