code: def test_boundaries_constant_image(mode):
      """A constant-valued image has not boundaries."""
      ones = np.ones((8, 8), dtype=int)
      b = find_boundaries(ones, mode=mode)
      assert np.all(b == 0)
  
file_path: scikit-image/skimage/segmentation/tests/test_boundaries.py
imports: import numpy
  import pytest
  from numpy.testing import assert_array_equal, assert_allclose
  from skimage._shared.utils import _supported_float_type
  from skimage.segmentation import find_boundaries, mark_boundaries
label_desc: Use image node_id 6 for calling a global function with example usage: test_boundaries_constant_image(mode) without return types