return nodeConnections.unmodifiableKeySet();
  }

  @Override
  public Set<E> edges() {
    return edgeToReferenceNode.unmodifiableKeySet();
  }

  @Override
  public boolean isDirected() {
    return isDirected;
  }

  @Override
  public boolean allowsParallelEdges() {
    return allowsParallelEdges;
  }

  @Override
  public boolean allowsSelfLoops() {
    return allowsSelfLoops;

     * that edge to {@code value} (overwriting the existing value, if any).
     *
     * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
     * undirected.
     *
     * <p>If this graph is directed, {@code endpoints} must be ordered.
     *
     * <p>Values do not have to be unique. However, values must be non-null.
     *

 *
 * <ul>
 *   <li>Test cases related to whether the graph is directed, undirected, mutable, or immutable.
 *   <li>Test cases related to the specific implementation of the {@link Network} interface.
 * </ul>
 *
 * TODO(user): Make this class generic (using <N, E>) for all node and edge types.
 * TODO(user): Differentiate between directed and undirected edge strings.
 */
public abstract class AbstractNetworkTest {

  private static MutableGraph<Integer> createGraph(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return GraphBuilder.undirected().allowsSelfLoops(true).build();
      case DIRECTED:
        return GraphBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  private static EdgeType oppositeType(EdgeType edgeType) {

  private static MutableGraph<Integer> createGraph(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return GraphBuilder.undirected().allowsSelfLoops(true).build();
      case DIRECTED:
        return GraphBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  private static EdgeType oppositeType(EdgeType edgeType) {

- Kube-apiserver: redirect responses are no longer returned from backends by default. Set `--aggregator-reject-forwarding-redirect=false` to continue forwarding redirect responses. ([#112358](https://github.com/kubernetes/kubernetes/pull/112358), [@enj](https://github.com/enj)) [SIG API Machinery]

    ImmutableValueGraph<String, Integer> emptyGraph =
        ValueGraphBuilder.directed()
            .allowsSelfLoops(true)
            .nodeOrder(ElementOrder.<String>natural())
            .<String, Integer>immutable()
            .build();

    assertThat(emptyGraph.isDirected()).isTrue();
    assertThat(emptyGraph.allowsSelfLoops()).isTrue();

- Kube-apiserver: redirect responses are no longer returned from backends by default. Set `--aggregator-reject-forwarding-redirect=false` to continue forwarding redirect responses. ([#112359](https://github.com/kubernetes/kubernetes/pull/112359), [@enj](https://github.com/enj)) [SIG API Machinery]

  }

  private static MutableNetwork<Integer, String> createNetwork(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return NetworkBuilder.undirected().allowsSelfLoops(true).build();
      case DIRECTED:
        return NetworkBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  private static EdgeType oppositeType(EdgeType edgeType) {

  }

  private static MutableNetwork<Integer, String> createNetwork(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return NetworkBuilder.undirected().allowsSelfLoops(true).build();
      case DIRECTED:
        return NetworkBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  private static EdgeType oppositeType(EdgeType edgeType) {