code: def test_train(self):
      config = get_test_mlp_task_config()
      task = build_task(config)
      num_samples = 10
  
      for cache_sample in [True, False]:
          precise_batch_norm_hook = PreciseBatchNormHook(
              num_samples, cache_sample
          )
          task.set_hooks([precise_batch_norm_hook])
          task.prepare()
          trainer = ClassyTrainer()
          trainer.train(task)
  
file_path: ClassyVision/test/hooks_precise_batch_norm_hook_test.py
imports: import copy
  import torch
  import torch.nn
  from classy_vision.hooks import ClassyHook
  from classy_vision.hooks.precise_batch_norm_hook import PreciseBatchNormHook
  from classy_vision.tasks import build_task
  from classy_vision.trainer import ClassyTrainer
  from test.generic.config_utils import get_test_mlp_task_config
  from test.generic.hook_test_utils import HookTestBase
label_desc: Use image node_id 4 for calling the TestPreciseBatchNormHook obj's underlying member method code with example usage: obj.test_train() without return types