class_docstr: Tests state_dict and load_state_dict
code: def _test_ddp(self, use_composable: bool) -> None:
      def init_model_optim():
          orig_model = CompositeParamModel(device=torch.device("cuda"))
          orig_optim = torch.optim.Adam(
              orig_model.parameters(), lr=1e-3
          )
          copy_optim = torch.optim.Adam(
              orig_model.parameters(), lr=1e-3
          )
          if use_composable:
              dist_model = replicate(copy.deepcopy(orig_model))
          else:
              dist_model = DDP(copy.deepcopy(orig_model))
          dist_optim = torch.optim.Adam(
              dist_model.parameters(), lr=1e-3
          )
          return (
              orig_model,
              orig_optim,
              copy_optim,
              dist_model,
              dist_optim,
          )
  
      self._test_save_load(init_model_optim)
  
imports: import copy
  import sys
  from itertools import chain
  from typing import Callable, Tuple
  import torch
  import torch.distributed
  import torch.nn
  from torch.distributed._composable import fully_shard, replicate
  from torch.distributed._shard.sharded_tensor import ShardedTensor
  from torch.distributed._tensor import DTensor, init_device_mesh
  from torch.distributed.checkpoint.state_dict import _patch_model_state_dict, _patch_optimizer_state_dict, get_model_state_dict, get_state_dict, set_model_state_dict, set_state_dict, StateDictOptions
  from torch.distributed.fsdp import FullyShardedDataParallel
  from torch.distributed.fsdp.wrap import ModuleWrapPolicy
  from torch.distributed.optim import _apply_optimizer_in_backward
  from torch.nn.parallel import DistributedDataParallel
  from torch.testing._internal.common_dist_composable import CompositeParamModel, UnitModule
  from torch.testing._internal.common_distributed import skip_if_lt_x_gpu
  from torch.testing._internal.common_utils import run_tests, TEST_WITH_DEV_DBG_ASAN
  from torch.testing._internal.distributed._tensor.common_dtensor import DTensorTestBase, with_comms
  from torch.testing._internal.distributed.common_state_dict import VerifyStateDictMixin
  from torch.utils._pytree import tree_all, tree_all_only
label_desc: Use image node_id 5 for calling the TestStateDict obj's underlying member method code with example usage: obj._test_ddp(use_composable) and returns: orig_model,  orig_optim,  copy_optim,  dist_model,  dist_optim