SortedAsMapView(SortedSet<K> set, Function<? super K, V> function) {
      super(set, function);
    }

    @Override
    SortedSet<K> backingSet() {
      return (SortedSet<K>) super.backingSet();
    }

    @Override
    @CheckForNull
    public Comparator<? super K> comparator() {
      return backingSet().comparator();
    }

    @Override