code: def mtotal_from_tau0_tau3(tau0, tau3, f_lower,
                            in_seconds=False):
      r
      mtotal = (tau3 / _a3(f_lower)) / (tau0 / _a0(f_lower))
      if not in_seconds:
          # convert back to solar mass units
          mtotal /= lal.MTSUN_SI
      return mtotal
docs: r"""Returns total mass from :math:`\tau_0, \tau_3`.