* not be updated after modifications to {@code graph}.
   *
   * @throws IllegalArgumentException if {@code node} is not present in {@code graph}
   * @since 33.1.0 (present with return type {@code Set} since 20.0)
   */
  public static <N> ImmutableSet<N> reachableNodes(Graph<N> graph, N node) {
    checkArgument(graph.nodes().contains(node), NODE_NOT_IN_GRAPH, node);

        assertThat(graph.degree(node)).isEqualTo(graph.adjacentNodes(node).size() + selfLoopCount);
        assertThat(graph.predecessors(node)).isEqualTo(graph.adjacentNodes(node));
        assertThat(graph.successors(node)).isEqualTo(graph.adjacentNodes(node));
        assertThat(graph.inDegree(node)).isEqualTo(graph.degree(node));
        assertThat(graph.outDegree(node)).isEqualTo(graph.degree(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);
  }

  final NetworkConnections<N, E> checkedConnections(N node) {
    NetworkConnections<N, E> connections = nodeConnections.get(node);
    if (connections == null) {

  }

  @Override
  public int degree(N node) {
    if (isDirected()) {
      return IntMath.saturatedAdd(inEdges(node).size(), outEdges(node).size());
    } else {
      return IntMath.saturatedAdd(incidentEdges(node).size(), edgesConnecting(node, node).size());
    }
  }

  @Override
  public int inDegree(N node) {
    return isDirected() ? inEdges(node).size() : degree(node);
  }

  @Override

 * graphs. Instances of this class should be constructed with {@link GraphBuilder}.
 *
 * <p>Time complexities for mutation methods are all O(1) except for {@code removeNode(N node)},
 * which is in O(d_node) where d_node is the degree of {@code node}.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 */
@ElementTypesAreNonnullByDefault
final class StandardMutableGraph<N> extends ForwardingGraph<N> implements MutableGraph<N> {

    if (predecessors != null) {
      checkState(predecessors.remove(node));
    }
    return node;
  }

  @Override
  public N removeOutEdge(E edge) {
    N node = super.removeOutEdge(edge);
    Multiset<N> successors = getReference(successorsReference);
    if (successors != null) {
      checkState(successors.remove(node));
    }
    return node;
  }

  @Override

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

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

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

      @Override

  static final String EDGE_NOT_IN_GRAPH = "Edge %s is not an element of this graph.";
  static final String NODE_REMOVED_FROM_GRAPH =
      "Node %s that was used to generate this set is no longer in the graph.";
  static final String NODE_PAIR_REMOVED_FROM_GRAPH =
      "Node %s or node %s that were used to generate this set are no longer in the graph.";
  static final String EDGE_REMOVED_FROM_GRAPH =

    AbstractGraphTest.validateGraph(transpose);

    for (Integer node : directedGraph.nodes()) {
      assertThat(directedGraph.inDegree(node)).isSameInstanceAs(transpose.outDegree(node));
      assertThat(directedGraph.outDegree(node)).isSameInstanceAs(transpose.inDegree(node));
    }

    assertThat(transpose.successors(N1)).doesNotContain(N2);
    directedGraph.putEdge(N2, N1);

    for (Integer node : graph.nodes()) {
      assertThat(graph.adjacentNodes(node)).isEqualTo(asGraph.adjacentNodes(node));
      assertThat(graph.predecessors(node)).isEqualTo(asGraph.predecessors(node));
      assertThat(graph.successors(node)).isEqualTo(asGraph.successors(node));
      assertThat(graph.degree(node)).isEqualTo(asGraph.degree(node));
      assertThat(graph.inDegree(node)).isEqualTo(asGraph.inDegree(node));