code: def test_zero_image(self):
      image = numpy.asarray(
          [[0, 0, 0], [0, 0, 0], [0, 0, 0]], dtype=float
      )
      self.__test_all_on_image(image)
  
imports: import unittest
  import numpy
  from numpy.testing import assert_array_equal
  from medpy.graphcut import graph_from_voxels
  from medpy.graphcut.energy_voxel import boundary_difference_linear, boundary_difference_exponential, boundary_difference_division, boundary_difference_power, boundary_maximum_linear, boundary_maximum_exponential, boundary_maximum_division, boundary_maximum_power, regional_probability_map
label_desc: Use image node_id 12 for calling the TestEnergyVoxel obj's underlying member method code with example usage: obj.test_zero_image() without return types