code: def sigma2_R(self, R, kwargs_mass, kwargs_light, kwargs_anisotropy):
          
          I_R_sigma2 = self.I_R_simga2(R, kwargs_mass, kwargs_light, kwargs_anisotropy)
          I_R = self.lightProfile.light_2d(R, kwargs_light)
          return I_R_sigma2 / I_R
docs: returns unweighted los velocity dispersion for a specified projected radius
  
          :param R: 2d projected radius (in angular units)
          :param kwargs_mass: mass model parameters (following lenstronomy lens model conventions)
          :param kwargs_light: deflector light parameters (following lenstronomy light model conventions)
          :param kwargs_anisotropy: anisotropy parameters, may vary according to anisotropy type chosen.
              We refer to the Anisotropy() class for details on the parameters.
          :return: