* #successors(Object)} and {@link #incidentEdges(Object)}.
   *
   * @since 29.0
   */
  @Override
  ElementOrder<N> incidentEdgeOrder();

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this graph.
   *

    public E last() {
      SortedSet<E> sortedUnfiltered = (SortedSet<E>) unfiltered;
      while (true) {
        E element = sortedUnfiltered.last();
        if (predicate.apply(element)) {
          return element;
        }
        sortedUnfiltered = sortedUnfiltered.headSet(element);
      }
    }
  }

  @GwtIncompatible // NavigableSet

  public Collection<V> removeAll(@Nullable Object key) {
    return containsKey(key) ? unfiltered.removeAll(key) : unmodifiableEmptyCollection();
  }

  @SuppressWarnings("EmptyList") // ImmutableList doesn't support nullable element types
  Collection<V> unmodifiableEmptyCollection() {
    if (unfiltered instanceof SetMultimap) {
      return emptySet();
    } else {
      return emptyList();
    }
  }

  @Override

  public Collection<V> removeAll(@Nullable Object key) {
    return containsKey(key) ? unfiltered.removeAll(key) : unmodifiableEmptyCollection();
  }

  @SuppressWarnings("EmptyList") // ImmutableList doesn't support nullable element types
  Collection<V> unmodifiableEmptyCollection() {
    if (unfiltered instanceof SetMultimap) {
      return emptySet();
    } else {
      return emptyList();
    }
  }

  @Override

   * extends AbstractListTester.) We could also iterate over all elements to
   * verify absence
   */
  protected void expectMissing(E... elements) {
    for (E element : elements) {
      assertFalse("Should not contain " + element, actualContents().contains(element));
    }
  }

  protected E[] createSamplesArray() {
    E[] array = getSubjectGenerator().createArray(getNumElements());
    getSampleElements().toArray(array);

   *
   * @throws IllegalArgumentException if {@code node} is not an element of this network
   */
  @Override
  int outDegree(N node);

  /**
   * Returns the nodes which are the endpoints of {@code edge} in this network.
   *
   * @throws IllegalArgumentException if {@code edge} is not an element of this network
   */
  EndpointPair<N> incidentNodes(E edge);

  /**

   */
  ALLOWS_NULL_QUERIES,
  ALLOWS_NULL_VALUES(ALLOWS_NULL_QUERIES),

  /**
   * Indicates that a collection disallows certain elements (other than {@code null}, whose validity
   * as an element is indicated by the presence or absence of {@link #ALLOWS_NULL_VALUES}). From the
   * documentation for {@link Collection}:
   *
   * <blockquote>
   *

    for (int i = 0; i < getNumElements(); i++) {
      assertTrue(
          "toArray(overSizedE[]) should contain element " + expectedSubArray[i],
          subArray.contains(expectedSubArray[i]));
    }
    assertNull(
        "The array element immediately following the end of the collection should be nulled",
        array[getNumElements()]);

   * support concurrent multisets whose content may change while the method is running.
   *
   * <p>The serialized output consists of the number of distinct elements, the first element, its
   * count, the second element, its count, and so on.
   */
  static <E extends @Nullable Object> void writeMultiset(
      Multiset<E> multiset, ObjectOutputStream stream) throws IOException {

    @Override
    public int count(@Nullable Object element) {
      return standardCount(element);
    }

    @Override
    public boolean equals(@Nullable Object object) {
      return standardEquals(object);
    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

    @Override
    public boolean add(E element) {
      return standardAdd(element);
    }