code: def test_video_classification_app_train_with_precise_bn(
      self, root_dir: str
  ) -> None:
      train_app = self.get_train_app(
          root_dir=root_dir, precise_bn_num_batches=2, logger=False
      )
      output = train_app.train()
      self.assertIsNotNone(output)
  
file_path: pytorchvideo/pytorchvideo_trainer/tests/test_task_video_classification.py
imports: from torchrecipes.core.base_train_app import BaseTrainApp
  from util import BaseTrainAppTestCase, create_small_kinetics_dataset, run_locally, tempdir
label_desc: Use image node_id 3 for calling the TestVideoClassificationTrainApp obj's underlying member method code with example usage: obj.test_video_classification_app_train_with_precise_bn(root_dir) without return types