code: def test_normalize_images(self):
      assert normalization.normalize_images(None) is None
  
      arr = np.zeros((1, 4, 4, 3), dtype=np.uint8)
      observed = normalization.normalize_images(arr)
      assert ia.is_np_array(observed)
      assert observed.shape == (1, 4, 4, 3)
      assert observed.dtype.name == "uint8"
  
      arr = np.zeros((1, 4, 4), dtype=np.uint8)
      observed = normalization.normalize_images(arr)
      assert ia.is_np_array(observed)
      assert observed.shape == (1, 4, 4, 1)
      assert observed.dtype.name == "uint8"
  
      arr = np.zeros((4, 4), dtype=np.uint8)
      observed = normalization.normalize_images(arr)
      assert ia.is_np_array(observed)
      assert observed.shape == (1, 4, 4, 1)
      assert observed.dtype.name == "uint8"
  
      observed = normalization.normalize_images([])
      assert isinstance(observed, list)
      assert len(observed) == 0
  
      arr1 = np.zeros((4, 4), dtype=np.uint8)
      arr2 = np.zeros((5, 5, 3), dtype=np.uint8)
      observed = normalization.normalize_images([arr1, arr2])
      assert isinstance(observed, list)
      assert len(observed) == 2
      assert ia.is_np_array(observed[0])
      assert ia.is_np_array(observed[1])
      assert observed[0].shape == (4, 4, 1)
      assert observed[1].shape == (5, 5, 3)
      assert observed[0].dtype.name == "uint8"
      assert observed[1].dtype.name == "uint8"
  
      with self.assertRaises(ValueError):
          normalization.normalize_images(False)
  
imports: from __future__ import print_function, division, absolute_import
  import sys
  import numpy
  import six.moves
  import imgaug
  import imgaug.augmentables.normalization
  from imgaug.testutils import reseed
label_desc: Use image node_id 9 for calling the TestNormalization obj's underlying member method code with example usage: obj.test_normalize_images() without return types