code: def test_3d_fallback_default_footprint():
      # 3x3x3 cube inside a 7x7x7 image:
      image = np.zeros((7, 7, 7), bool)
      image[2:-2, 2:-2, 2:-2] = 1
  
      opened = binary.binary_opening(image)
  
      # expect a "hyper-cross" centered in the 5x5x5:
      image_expected = np.zeros((7, 7, 7), dtype=bool)
      image_expected[2:5, 2:5, 2:5] = ndi.generate_binary_structure(
          3, 1
      )
      assert_array_equal(opened, image_expected)
  
imports: import numpy
  import pytest
  from numpy.testing import assert_array_equal, assert_equal
  from scipy import ndimage
  from skimage import data, color, morphology
  from skimage.util import img_as_bool
  from skimage.morphology import binary, footprints, gray
label_desc: Use image node_id 20 for calling a global function with example usage: test_3d_fallback_default_footprint() without return types