/**
 * A {@link ListMultimap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)