docs: def Bern_to_Fierz_nunu(C,ddll):
      """From semileptonic Bern basis to Fierz semileptonic basis for Class V.
      C should be the corresponding leptonic Fierz basis and
      `ddll` should be of the form 'sbl_enu_tau', 'dbl_munu_e' etc."""
      ind = ddll.replace('l_','').replace('nu_','')
      return {
              'F' + ind + 'nu': C['nu1' + ind],
              'F' + ind + 'nup': C['nu1p' + ind],
              }