code: def test_all_data(self):
      folder = "testing_data"
      all_files = [
          os.path.join(folder, f)
          for f in os.listdir(folder)
          if os.path.isfile(os.path.join(folder, f))
      ]
  
      for f in all_files:
          if f.endswith("nii.gz"):
              loaded_shape = (
                  image_loader.load_image_obj(f).get_data().shape
              )
              print(loaded_shape)
              self.assertGreaterEqual(5, len(loaded_shape))
          else:
              with self.assertRaisesRegexp(ValueError, ""):
                  image_loader.load_image_obj(f)
  
file_path: NiftyNet/tests/image_loader_test.py
imports: from __future__ import absolute_import, print_function
  import os
  import numpy
  import tensorflow
  import niftynet.io.image_loader
  from tests.niftynet_testcase import NiftyNetTestCase
label_desc: Use image node_id 5 for calling the ImageLoaderTest obj's underlying member method code with example usage: obj.test_all_data() without return types