code: def test_no_channel(self):
      with tempfile.TemporaryDirectory() as tempdir:
          fname = os.path.join(tempdir, "testing.nii.gz")
          writer = ITKWriter(output_dtype=np.uint8)
          writer.set_data_array(
              np.arange(48).reshape(3, 4, 4), channel_dim=None
          )
          writer.write(fname)
  
          output = np.asarray(itk.imread(fname))
          np.testing.assert_allclose(output.shape, (4, 4, 3))
          np.testing.assert_allclose(output[1, 1], (5, 21, 37))
  
file_path: MONAI/tests/test_itk_writer.py
imports: from __future__ import annotations
  import os
  import tempfile
  import unittest
  import numpy
  import torch
  from monai.data import ITKWriter
  from monai.utils import optional_import
label_desc: Use image node_id 3 for calling the TestITKWriter obj's underlying member method code with example usage: obj.test_no_channel() without return types