* @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public class TreeMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractSortedKeySortedSetMultimap<K, V> {
  private transient Comparator<? super K> keyComparator;
  private transient Comparator<? super V> valueComparator;

  /**