Multimap<? extends K, ? extends V> multimap) {
    this(keyComparator, valueComparator);
    putAll(multimap);
  }

  @Override
  Map<K, Collection<V>> createAsMap() {
    return createMaybeNavigableAsMap();
  }

  /**
   * {@inheritDoc}
   *
   * <p>Creates an empty {@code TreeSet} for a collection of values for one key.
   *

  }

  @Override
  Map<K, Collection<V>> createAsMap() {
    return new AsMap(map);
  }

  final Map<K, Collection<V>> createMaybeNavigableAsMap() {
    if (map instanceof NavigableMap) {
      return new NavigableAsMap((NavigableMap<K, Collection<V>>) map);
    } else if (map instanceof SortedMap) {

    }

    @Override
    Set<K> createKeySet() {
      return createMaybeNavigableKeySet();
    }

    @Override
    Map<K, Collection<V>> createAsMap() {
      return createMaybeNavigableAsMap();
    }

    @Override
    protected Collection<V> createCollection() {
      return factory.get();
    }

    @Override