code: def test_initialize_after_switching(self):
      # This simulates the resumption after the switching.
      runner = Mock()
      runner.model = Mock()
      runner.model.module = Mock()
      runner.train_dataloader = Mock()
      runner.train_dataloader.persistent_workers = True
      runner.train_dataloader._DataLoader__initialized = True
  
      stage2 = [dict(type="RandomResize", scale=(1280, 1280))]
  
      runner.epoch = 286  # epoch > switch_epoch
      hook = PipelineSwitchHook(
          switch_epoch=285, switch_pipeline=stage2
      )
      hook.before_train_epoch(runner)
      self.assertTrue(hook._restart_dataloader)
      self.assertFalse(runner.train_dataloader._DataLoader__initialized)
      self.assertTrue(
          len(runner.train_dataloader.dataset.pipeline.transforms) == 1
      )
  
file_path: mmdetection/tests/test_engine/test_hooks/test_pipeline_switch_hook.py
imports: from unittest import TestCase
  from unittest.mock import Mock
  from mmdet.engine.hooks import PipelineSwitchHook
label_desc: Use image node_id 3 for calling the TestPipelineSwitchHook obj's underlying member method code with example usage: obj.test_initialize_after_switching() without return types