code: def test_H2(self):
      h = haralick.Haralick(gray, labels, 0, 1, nlevels=4)
      self.assertAlmostEqual(h.H2()[0], 0.5833, 4)
  
imports: import unittest
  import centrosome.haralick
  import numpy
label_desc: Use image node_id 6 for calling the TestHaralick obj's underlying member method code with example usage: obj.test_H2() without return types