code: def mass_tot(self, rho0, Ra, Rs):
          
          Ra, Rs = self._sort_ra_rs(Ra, Rs)
          sigma0 = self.rho2sigma(rho0, Ra, Rs)
          m_tot = 2 * np.pi * sigma0 * Ra * Rs
          return m_tot
docs: total mass within the profile
          :param rho0:
          :param Ra:
          :param Rs:
          :return: