public enum SetMultimapImpl {
    HashMultimapImpl {
      @Override
      <K extends Comparable<K>, V extends Comparable<V>> SetMultimap<K, V> create(
          Multimap<K, V> contents) {
        return HashMultimap.create(contents);
      }
    },
    LinkedHashMultimapImpl {
      @Override
      <K extends Comparable<K>, V extends Comparable<V>> SetMultimap<K, V> create(
          Multimap<K, V> contents) {

  }

  /** Test that creating one TreeMultimap from a non-TreeMultimap results in natural ordering. */
  public void testCreateFromHashMultimap() {
    Multimap<Double, Double> hash = HashMultimap.create();
    hash.put(1.0, 2.0);
    hash.put(2.0, 3.0);
    hash.put(3.0, 4.0);
    hash.put(4.0, 5.0);

    TreeMultimap<Double, Double> copyFromHash = TreeMultimap.create(hash);

  }

  /** Test that creating one TreeMultimap from a non-TreeMultimap results in natural ordering. */
  public void testCreateFromHashMultimap() {
    Multimap<Double, Double> hash = HashMultimap.create();
    hash.put(1.0, 2.0);
    hash.put(2.0, 3.0);
    hash.put(3.0, 4.0);
    hash.put(4.0, 5.0);

    TreeMultimap<Double, Double> copyFromHash = TreeMultimap.create(hash);

 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multimap">{@code Multimap}</a>.
 *
 * @author Jared Levy
 * @since 2.0
 */
@DoNotMock("Use ImmutableMultimap, HashMultimap, or another implementation")
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface Multimap<K extends @Nullable Object, V extends @Nullable Object> {
  // Query Operations

  /**

   * #synchronizedMultimap}.
   *
   * <p>Call this method only when the simpler methods {@link ArrayListMultimap#create()}, {@link
   * HashMultimap#create()}, {@link LinkedHashMultimap#create()}, {@link
   * LinkedListMultimap#create()}, {@link TreeMultimap#create()}, and {@link
   * TreeMultimap#create(Comparator, Comparator)} won't suffice.
   *