class_docstr: Test the Tamura Texture features programmed in medpy.features.texture.
  Functions are:  coarseness(image, voxelspacing = None, mask = slice(None))
                  contrast(image, mask = slice(None))
                  directionality(image, voxelspacing = None, mask = slice(None), min_distance = 4)
code: def test_Contrast(self):
      standard_deviation = numpy.std(self.image1)
      kurtosis = stats.kurtosis(
          self.image1, axis=None, bias=True, fisher=False
      )
      Fcon1 = standard_deviation / (kurtosis**0.25)
  
      res = contrast(self.image1)
      self.assertEqual(
          res,
          Fcon1,
          "contrast: 2D image, no mask: got {} ,expected {}".format(
              res, Fcon1
          ),
      )
  
      image2 = self.image1[0:50, 0:50]
      standard_deviation = numpy.std(image2)
      kurtosis = stats.kurtosis(
          image2, axis=None, bias=True, fisher=False
      )
      Fcon2 = standard_deviation / (kurtosis**0.25)
  
      res = contrast(self.image1, mask=self.mask1)
      self.assertEqual(
          res,
          Fcon2,
          "contrast: 2D image, mask = [slice(0,50,1), slice(0,50,1)]: got {} ,expected {}".format(
              res, Fcon2
          ),
      )
  
file_path: medpy/tests/features_/texture.py
imports: import unittest
  from medpy.features.texture import *
label_desc: Use image node_id 3 for calling the TestTextureFeatures obj's underlying member method code with example usage: obj.test_Contrast() without return types