code: def on_train_batch_start(self, trainer, model, batch, batch_idx):
      rank = trainer.local_rank
      assert isinstance(model, TopModule)
      # index = None also means first device
      assert (
          model.device.index is None and rank == 0
      ) or model.device.index == rank
      assert model.device == model.module.module.device
  
file_path: pytorch-lightning/tests/tests_pytorch/utilities/test_dtype_device_mixin.py
imports: import torch.nn
  from lightning.fabric.utilities.device_dtype_mixin import _DeviceDtypeModuleMixin
  from lightning.pytorch import Callback, Trainer
  from lightning.pytorch.demos.boring_classes import BoringModel
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 1 for calling the DeviceAssertCallback obj's underlying member method code with example usage: obj.on_train_batch_start(trainer, model, batch, batch_idx) without return types