*/
  private static final class PopulatableMapAsMultimap<K, V> extends ForwardingMultimap<K, V> {
    final Map<K, V> map;
    final SetMultimap<K, V> unusableDelegate;

    static <K, V> PopulatableMapAsMultimap<K, V> create() {
      return new PopulatableMapAsMultimap<>();
    }

    @SuppressWarnings("unchecked") // all methods throw immediately
    PopulatableMapAsMultimap() {
      this.map = new HashMap<>();