code: def test_vertical_mask_line(grad_func):
      """Vertical edge filters mask pixels surrounding input mask."""
      _, hgrad = np.mgrid[
          :1:11j, :1:11j
      ]  # horizontal gradient with spacing 0.1
      hgrad[:, 5] = 1  # bad vertical line
  
      mask = np.ones_like(hgrad)
      mask[:, 5] = 0  # mask bad line
  
      expected = np.zeros_like(hgrad)
      expected[1:-1, 1:-1] = 0.2  # constant gradient for most of image,
      expected[1:-1, 4:7] = 0  # but line and neighbors masked
  
      result = grad_func(hgrad, mask)
      assert_allclose(result, expected)
  
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 56 for calling a global function with example usage: test_vertical_mask_line(grad_func) without return types