code: @Beta
    public ImmutableSetMultimap<K, V> asMultimap() {
      ImmutableSetMultimap<K, V> result = multimapView;
      return (result == null)
          ? (multimapView = new ImmutableSetMultimap<K, V>(
              new MapViewOfValuesAsSingletonSets(), size(), null))
          : result;
    }
docs: Returns a multimap view of the map.
  
  @since 14.0