code: def mass_3d_lens(self, r, theta_E, gamma, e1, e2):
          
          return self.spp.mass_3d_lens(r, theta_E, gamma)
docs: computes the spherical power-law mass enclosed (with SPP routiune)
          :param r:
          :param theta_E:
          :param gamma:
          :param q:
          :param phi_G:
          :return: