code: def test_scharr_v_horizontal():
      """vertical Scharr on a horizontal edge should be zero."""
      i, j = np.mgrid[-5:6, -5:6]
      image = (i >= 0).astype(float)
      result = filters.scharr_v(image)
      assert_allclose(result, 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 28 for calling a global function with example usage: test_scharr_v_horizontal() without return types