docs: def _FlavioI_to_Bern_I(C, qq):
      """From FlavioI to BernI basis for $\Delta F=2$ operators.
      `qq` should be 'sb', 'db', 'ds' or 'uc'"""
      qqb = qq[::-1]  # flavio uses "bs" instead of "sb" etc.
      if qq in ['bs', 'bd', 'sd', 'uc']:
          return {
              '1' + 2*qqb: C["CVLL_" + 2*qq],
              '2' + 2*qqb: C["CSLL_" + 2*qq] - 4 * C["CTLL_" + 2*qq],
              '3' + 2*qqb: -8 * C["CTLL_" + 2*qq],
              '4' + 2*qqb: C["CSLR_" + 2*qq],
              '5' + 2*qqb: -2 * C["CVLR_" + 2*qq],
              '1p' + 2*qqb: C["CVRR_" + 2*qq],
              '2p' + 2*qqb: C["CSRR_" + 2*qq] - 4 * C["CTRR_" + 2*qq],
              '3p' + 2*qqb: -8 * C["CTRR_" + 2*qq],
              }
      else:
          raise ValueError("not in Bern_I: ".format(qq))