* @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public final class HashMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends HashMultimapGwtSerializationDependencies<K, V> {
  private static final int DEFAULT_VALUES_PER_KEY = 2;

  @VisibleForTesting transient int expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;

  /**