docs: def JMS_to_Fierz_nunu(C, ddll):
      """From JMS to semileptonic Fierz basis for Class V.
      `ddll` should be of the form 'sbl_enu_tau', 'dbl_munu_e' etc."""
      s = dflav[ddll[0]]
      b = dflav[ddll[1]]
      l = lflav[ddll[4:ddll.find('n')]]
      lp = lflav[ddll[ddll.find('_',5)+1:len(ddll)]]
      ind = ddll.replace('l_','').replace('nu_','')
      return {
          'F' + ind + 'nu' : C["VnudLL"][l, lp, s, b],
          'F' + ind + 'nup' : C["VnudLR"][l, lp, s, b]
          }