private class SortedAsMap extends AsMap implements SortedMap<K, Collection<V>> {
    SortedAsMap(SortedMap<K, Collection<V>> submap) {
      super(submap);
    }

    SortedMap<K, Collection<V>> sortedMap() {
      return (SortedMap<K, Collection<V>>) submap;
    }

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

  private class SortedAsMap extends AsMap implements SortedMap<K, Collection<V>> {
    SortedAsMap(SortedMap<K, Collection<V>> submap) {
      super(submap);
    }

    SortedMap<K, Collection<V>> sortedMap() {
      return (SortedMap<K, Collection<V>>) submap;
    }

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