code: def on_train_start(self):
      assert (
          self.trainer.estimated_stepping_batches
          == len(self.train_dataloader()) // self.trainer.world_size
      )
  
imports: import logging
  import os
  from unittest import mock
  import pytest
  import torch
  from lightning.pytorch import Trainer
  from lightning.pytorch.demos.boring_classes import BoringModel, RandomIterableDataset
  from lightning.pytorch.strategies import SingleDeviceXLAStrategy
  from torch.utils.data import DataLoader
  from tests_pytorch.conftest import mock_cuda_count
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 1 for calling the MultiprocessModel obj's underlying member method code with example usage: obj.on_train_start() without return types