code: def pareto_set(self, *args, **kwargs):
          
          if self._pareto_set is None:
              self._pareto_set = self._calc_pareto_set(*args, **kwargs)
  
          return self._pareto_set
docs: Returns
          -------
          S : np.array
              Returns the pareto set for a problem. Points in the X space to be known to be optimal!