code: def test_sobel_vertical():
      """Sobel on a vertical edge should be a vertical line."""
      i, j = np.mgrid[-5:6, -5:6]
      image = (j >= 0).astype(float)
      result = filters.sobel(image) * np.sqrt(2)
      assert np.all(result[j == 0] == 1)
      assert np.all(result[np.abs(j) > 1] == 0)
  
imports: import numpy
  import pytest
  from numpy.testing import assert_, assert_allclose, assert_array_almost_equal
  from skimage import data, filters
  from skimage._shared.utils import _supported_float_type
  from skimage.filters.edges import _mask_filter_result
label_desc: Use image node_id 8 for calling a global function with example usage: test_sobel_vertical() without return types