code: def _l_cv_and_skew(self, catchment):
          
          z = self._dimensionless_flows(catchment)
          l1, l2, t3 = lm.lmom_ratios(z, nmom=3)
          return l2 / l1, t3
docs: Calculate L-CV and L-SKEW for a gauged catchment. Uses `lmoments3` library.
  
          Methodology source: Science Report SC050050, para. 6.7.5