code: def on_train_start(self) -> None:
      # assert strategy attributes for device setting
      assert self.device == torch.device("xla", index=0)
      assert os.environ.get("PT_XLA_DEBUG") == "1"
  
file_path: pytorch-lightning/tests/tests_pytorch/strategies/test_xla.py
imports: import os
  from unittest import mock
  from unittest.mock import Mock
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.accelerators import XLAAccelerator
  from lightning.pytorch.demos.boring_classes import BoringModel
  from lightning.pytorch.strategies import XLAStrategy
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 1 for calling the BoringModelTPU obj's underlying member method code with example usage: obj.on_train_start() without return types