code: def test_ddp_module_state_dict():
      """Test that the module state dict can be retrieved and loaded without the prefixed wrapper keys from DDP."""
  
      class DistributedDataParallelMock(MagicMock):
          def __instancecheck__(self, instance):
              # to make the strategy's `isinstance(model, DistributedDataParallel)` pass with a mock as class
              return True
  
      strategy = DDPStrategy(
          parallel_devices=[torch.device("cpu"), torch.device("cpu")]
      )
  
      # Without DDP applied (no setup call)
      original_module = torch.nn.Linear(2, 3)
      original_state_dict = deepcopy(original_module.state_dict())
      retrieved_state_dict = strategy.get_module_state_dict(
          original_module
      )
      assert retrieved_state_dict.keys() == original_state_dict.keys()
      strategy.load_module_state_dict(
          original_module, retrieved_state_dict
      )
  
      # With DDP applied (setup called)
      with mock.patch(
          "lightning.fabric.strategies.ddp.DistributedDataParallel",
          DistributedDataParallelMock,
      ):
          wrapped_module = strategy.setup_module(original_module)
          retrieved_state_dict = strategy.get_module_state_dict(
              wrapped_module
          )
      assert retrieved_state_dict.keys() == original_state_dict.keys()
      strategy.load_module_state_dict(
          wrapped_module, retrieved_state_dict
      )
      strategy.load_module_state_dict(
          wrapped_module, original_state_dict
      )
  
imports: import os
  from copy import deepcopy
  from datetime import timedelta
  from unittest import mock
  from unittest.mock import MagicMock, Mock
  import pytest
  import torch
  from lightning.fabric.plugins import DoublePrecision, HalfPrecision, Precision
  from lightning.fabric.plugins.environments import LightningEnvironment
  from lightning.fabric.strategies import DDPStrategy
  from lightning.fabric.strategies.ddp import _DDPBackwardSyncControl
  from lightning.fabric.utilities.imports import _TORCH_GREATER_EQUAL_2_0
  from torch.nn.parallel import DistributedDataParallel
  from tests_fabric.helpers.runif import RunIf
label_desc: Use image node_id 4 for calling a global function with example usage: test_ddp_module_state_dict() and returns: True