*/
  public static <K extends @Nullable Object, V extends @Nullable Object>
      Multimap<K, V> unmodifiableMultimap(Multimap<K, V> delegate) {
    if (delegate instanceof UnmodifiableMultimap || delegate instanceof ImmutableMultimap) {
      return delegate;
    }
    return new UnmodifiableMultimap<>(delegate);
  }

  /**
   * Simply returns its argument.
   *
   * @deprecated no need to use this