code: def test_dataloader(self):
      dataset = Dataset(
          data=[
              {"img": np.array([[[0.0, 1.0], [2.0, 3.0]]])},
              {"img": np.array([[[0.0, 1.0], [2.0, 3.0]]])},
          ],
          transform=IntensityStatsd(
              keys="img", ops=["max", "mean"], key_prefix="orig"
          ),
      )
      # set num workers = 0 for mac / win
      num_workers = 2 if sys.platform == "linux" else 0
      dataloader = DataLoader(
          dataset=dataset, num_workers=num_workers, batch_size=2
      )
      orig_method = mp.get_start_method()
      mp.set_start_method("spawn", force=True)
  
      for d in dataloader:
          meta = d[PostFix.meta("img")]
          np.testing.assert_allclose(
              meta["orig_max"], [3.0, 3.0], atol=1e-3
          )
          np.testing.assert_allclose(
              meta["orig_mean"], [1.5, 1.5], atol=1e-3
          )
      # restore the mp method
      mp.set_start_method(orig_method, force=True)
  
file_path: MONAI/tests/test_intensity_statsd.py
imports: from __future__ import annotations
  import sys
  import unittest
  import numpy
  import torch.multiprocessing
  from parameterized import parameterized
  from monai.data import DataLoader, Dataset
  from monai.transforms import IntensityStatsd
  from monai.utils.enums import PostFix
label_desc: Use image node_id 2 for calling the TestIntensityStatsd obj's underlying member method code with example usage: obj.test_dataloader() without return types