code: def anisotropy(self):
          
          square_diff_energy = 0
          weighted_energy = self.weighted_surface_energy
          area_frac_dict = self.area_fraction_dict
          miller_energy_dict = self.miller_energy_dict
  
          for hkl in miller_energy_dict.keys():
              square_diff_energy += (miller_energy_dict[hkl] - weighted_energy)\
                                    ** 2 * area_frac_dict[hkl]
          return np.sqrt(square_diff_energy) / weighted_energy
docs: Returns:
              (float) Coefficient of Variation from weighted surface energy
              The ideal sphere is 0.