code: public static <C extends Comparable<? super C>>
  	Collector<C, ?, ParetoFront<C>> toParetoFront() {
  		return toParetoFront(Comparator.naturalOrder());
  	}
docs: Return a pareto-front collector. The natural order of the elements is
  used as pareto-dominance order.
  
  @param <C> the element type
  @return a new pareto-front collector