docs: def Fierz_to_Bern_nunu(C, ddll):
      """From semileptonic Fierz basis to Bern 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_','')
      dic = {
  
          'nu1' + ind : C['F' + ind + 'nu'],
          'nu1p' + ind : C['F' + ind + 'nup']
      }
      return dic