@Override
  public Set<N> predecessors() {
    return Collections.unmodifiableSet(predecessorsMultiset().elementSet());
  }

  private Multiset<N> predecessorsMultiset() {
    Multiset<N> predecessors = getReference(predecessorsReference);
    if (predecessors == null) {
      predecessors = HashMultiset.create(inEdgeMap.values());

  Set<EndpointPair<N>> edges();

  /**
   * Returns an {@link ElementOrder} that specifies the order of iteration for the elements of
   * {@link #edges()}, {@link #adjacentNodes(Object)}, {@link #predecessors(Object)}, {@link
   * #successors(Object)} and {@link #incidentEdges(Object)}.
   *
   * @since 29.0
   */
  ElementOrder<N> incidentEdgeOrder();

  /**

 * which has a method {@code getParents()} that retrieves its predecessors in a graph:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, MyNode::getParents);
 * }
 *
 * <p>If you have some other mechanism for returning the predecessors of a node, or one that doesn't
 * return a {@code Iterable<? extends N>}, then you can use a lambda to perform a more general

  /** Remove {@code node} from the set of predecessors. */
  void removePredecessor(N node);

  /**
   * Remove {@code node} from the set of successors. Returns the value previously associated with
   * the edge connecting the two nodes.
   */
  @CanIgnoreReturnValue
  @Nullable V removeSuccessor(N node);

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it

  @Override
  public Set<N> adjacentNodes(N node) {
    return nodeInvalidatableSet(checkedConnections(node).adjacentNodes(), node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return nodeInvalidatableSet(checkedConnections(node).predecessors(), node);
  }

  @Override
  public Set<N> successors(N node) {
    return nodeInvalidatableSet(checkedConnections(node).successors(), node);
  }

  @Override

                      Iterators.transform(
                          graph.predecessors(node).iterator(),
                          (N predecessor) -> EndpointPair.ordered(predecessor, node)),
                      Iterators.transform(
                          // filter out 'node' from successors (already covered by predecessors,
                          // above)

    return delegate().incidentEdgeOrder();
  }

  @Override
  public Set<N> adjacentNodes(N node) {
    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public int degree(N node) {

    return delegate().edgeOrder();
  }

  @Override
  public Set<N> adjacentNodes(N node) {
    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public Set<E> incidentEdges(N node) {

  @Override
  ElementOrder<N> nodeOrder();

  /**
   * Returns an {@link ElementOrder} that specifies the order of iteration for the elements of
   * {@link #edges()}, {@link #adjacentNodes(Object)}, {@link #predecessors(Object)}, {@link
   * #successors(Object)} and {@link #incidentEdges(Object)}.
   *
   * @since 29.0
   */
  @Override
  ElementOrder<N> incidentEdgeOrder();

  //
  // Element-level accessors

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this graph.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}
   * {@code view} returned by this method will be invalidated, and will throw {@code