code: def nfw_angle2physical(self, Rs_angle, theta_Rs):
          
          Rs = Rs_angle * const.arcsec * self.D_d
          theta_scaled = theta_Rs * self.epsilon_crit * self.D_d * const.arcsec
          rho0 = theta_scaled / (4 * Rs ** 2 * (1 + np.log(1. / 2.)))
          rho0_com = rho0 / self.h**2 * self.a_z(self.z_lens)**3
          c = self.nfw_param.c_rho0(rho0_com)
          r200 = c * Rs
          M200 = self.nfw_param.M_r200(r200 * self.h / self.a_z(self.z_lens)) / self.h
          return rho0, Rs, c, r200, M200
docs: converts the angular parameters into the physical ones for an NFW profile
  
          :param theta_Rs: observed bending angle at the scale radius in units of arcsec
          :param Rs: scale radius in units of arcsec
          :return: M200, r200, Rs_physical, c