code: def test_multiple_device_transfer(
      self, device, dtype, module_info, training
  ):
      module_cls = module_info.module_cls
      module_inputs_device = module_info.module_inputs_func(
          module_info,
          device=device,
          dtype=dtype,
          requires_grad=False,
          training=training,
      )
      module_inputs_cpu = module_info.module_inputs_func(
          module_info,
          device="cpu",
          dtype=dtype,
          requires_grad=False,
          training=training,
      )
      for module_input_device, module_input_cpu in zip(
          module_inputs_device, module_inputs_cpu
      ):
          if module_input_device.forward_input is None:
              continue
  
          with freeze_rng_state():
              # === Instantiate the module. ===
              args, kwargs = (
                  module_input_device.constructor_input.args,
                  module_input_device.constructor_input.kwargs,
              )
              m = module_cls(*args, **kwargs)
              m.to(device).to(dtype)
              m.train(training)
  
              # === Do forward pass on GPU ===
              input_device_args = module_input_device.forward_input.args
              input_device_kwargs = (
                  module_input_device.forward_input.kwargs
              )
              m(*input_device_args, **input_device_kwargs)
              self._assert_module_parameters_and_buffer_are(
                  m, device, dtype
              )
  
              # === Move to CPU ===
              input_cpu_args = module_input_cpu.forward_input.args
              input_cpu_kwargs = module_input_cpu.forward_input.kwargs
              m.cpu()
              m(*input_cpu_args, **input_cpu_kwargs)
              self._assert_module_parameters_and_buffer_are(
                  m, "cpu", dtype
              )
  
              # === Move back to GPU and forward pass ===
              m.cuda()
              m(*input_device_args, **input_device_kwargs)
              self._assert_module_parameters_and_buffer_are(
                  m, device, dtype
              )
  
              if torch.cuda.device_count() >= 2:
                  # === test cross-GPU transfer works
                  def _to_device1(objs):
                      if isinstance(objs, (tuple, list)):
                          return type(objs)(
                              _to_device1(item) for item in objs
                          )
                      elif isinstance(objs, dict):
                          return {
                              name: _to_device1(item)
                              for name, item in objs.items()
                          }
                      elif isinstance(objs, torch.Tensor):
                          return objs.cuda(1)
                      else:
                          return objs
  
                  input_device_1_args = _to_device1(input_device_args)
                  input_device_1_kwargs = _to_device1(
                      input_device_kwargs
                  )
  
                  m.cuda(1)
                  with torch.cuda.device(1):
                      m(*input_device_1_args, **input_device_1_kwargs)
                  self._assert_module_parameters_and_buffer_are(
                      m, torch.device("cuda:1"), dtype
                  )
  
imports: from itertools import chain, product
  from inspect import signature, isgenerator
  from copy import deepcopy
  import tempfile
  from operator import methodcaller
  import torch
  from torch._subclasses.meta_utils import assert_metadata_eq
  from torch.testing._internal.common_cuda import with_tf32_off
  from torch.testing._internal.common_device_type import instantiate_device_type_tests, onlyCPU, onlyCUDA, toleranceOverride, tol, skipMeta
  from torch.testing._internal.common_modules import module_db, modules, ModuleErrorEnum, TrainEvalMode
  from torch.testing._internal.common_utils import TestCase, run_tests, freeze_rng_state, mock_wrapper, get_tensors_from, gradcheck, gradgradcheck
  from unittest.mock import patch, call
label_desc: Use image node_id 4 for calling the TestModule obj's underlying member method code with example usage: obj.test_multiple_device_transfer(device, dtype, module_info, training) and returns: type, unknown, objs, objs