code: def test_channel_wise(self):
      key = "img"
      image = np.stack(
          (np.asarray([1.0, 2.0]), np.asarray([1.0, 1.0]))
      )  # std: 0.5, 0
      factor = np.random.rand()
      std_shifter = StdShiftIntensityd(
          keys=[key], factor=factor, channel_wise=True
      )
      result = std_shifter({key: image})
      expected = np.stack(
          (
              np.asarray([1 + 0.5 * factor, 2 + 0.5 * factor]),
              np.asarray([1, 1]),
          )
      )
      np.testing.assert_allclose(result[key], expected, rtol=1e-5)
  
file_path: MONAI/tests/test_std_shift_intensityd.py
imports: from __future__ import annotations
  import unittest
  import numpy
  from monai.transforms import ShiftIntensityd, StdShiftIntensityd
  from monai.utils import dtype_numpy_to_torch
  from tests.utils import NumpyImageTestCase2D
label_desc: Use image node_id 4 for calling the TestStdShiftIntensityd obj's underlying member method code with example usage: obj.test_channel_wise() without return types