code: def test_vary_lightness_threshold(self):
      # test when varying lightness_threshold between images
      image = (
          np.arange(0, 6 * 6 * 3).reshape((6, 6, 3)).astype(np.uint8)
      )
      image_hls = cv2.cvtColor(image, cv2.COLOR_RGB2HLS)
  
      aug = iaa.FastSnowyLandscape(
          lightness_threshold=_TwoValueParam(75, 125),
          lightness_multiplier=2.0,
      )
  
      mask = image_hls[..., 1] < 75
      expected1 = np.copy(image_hls).astype(np.float64)
      expected1[..., 1][mask] *= 2.0
      expected1 = np.clip(np.round(expected1), 0, 255).astype(np.uint8)
      expected1 = cv2.cvtColor(expected1, cv2.COLOR_HLS2RGB)
  
      mask = image_hls[..., 1] < 125
      expected2 = np.copy(image_hls).astype(np.float64)
      expected2[..., 1][mask] *= 2.0
      expected2 = np.clip(np.round(expected2), 0, 255).astype(np.uint8)
      expected2 = cv2.cvtColor(expected2, cv2.COLOR_HLS2RGB)
  
      observed = aug.augment_images([image] * 4)
  
      assert np.array_equal(observed[0], expected1)
      assert np.array_equal(observed[1], expected2)
      assert np.array_equal(observed[2], expected1)
      assert np.array_equal(observed[3], expected2)
  
imports: from __future__ import print_function, division, absolute_import
  import sys
  import numpy
  import cv2
  import imgaug
  from imgaug import augmenters
  from imgaug import parameters
  from imgaug.testutils import reseed, runtest_pickleable_uint8_img, is_parameter_instance
label_desc: Use image node_id 4 for calling the TestFastSnowyLandscape obj's underlying member method code with example usage: obj.test_vary_lightness_threshold() without return types