code: def forward(self, x):
      return self.net4(self.net3(self.net2(self.net1(x))))
  
file_path: pytorch/torch/distributed/checkpoint/examples/stateful_example.py
imports: import os
  import shutil
  import torch
  import torch.distributed
  import torch.multiprocessing
  import torch.nn
  from torch.distributed._tensor.device_mesh import init_device_mesh
  from torch.distributed.checkpoint.filesystem import _FileSystemCheckpointer
  from torch.distributed.checkpoint.state_dict import _patch_model_state_dict, _patch_optimizer_state_dict
  from torch.distributed.fsdp import FullyShardedDataParallel
label_desc: Use image node_id 2 for calling the Model obj's underlying member method code with example usage: obj.forward(x) and returns: self