}
    return new EntriesImpl();
  }

  @Override
  Iterator<Entry<K, V>> entryIterator() {
    throw new AssertionError("should never be called");
  }

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

  /**
   * @serialData the number of distinct keys, and then for each distinct key: the first key, the

      Entry<K, V> output(@ParametricNullness K key, @ParametricNullness V value) {
        return immutableEntry(key, value);
      }
    };
  }

  @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);

    checkNotNull(action);
    map.forEach(
        (key, valueCollection) -> valueCollection.forEach(value -> action.accept(key, value)));
  }

  @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);