}

  @Override
  public Set<E> edgesConnecting(N nodeU, N nodeV) {
    return delegate().edgesConnecting(nodeU, nodeV);
  }

  @Override
  public Set<E> edgesConnecting(EndpointPair<N> endpoints) {
    return delegate().edgesConnecting(endpoints);
  }

  @Override
  public Optional<E> edgeConnecting(N nodeU, N nodeV) {
    return delegate().edgeConnecting(nodeU, nodeV);
  }

  @Override

          + "so it cannot be reused to connect the following nodes: %s.";
  static final String MULTIPLE_EDGES_CONNECTING =
      "Cannot call edgeConnecting() when parallel edges exist between %s and %s. Consider calling "
          + "edgesConnecting() instead.";
  static final String PARALLEL_EDGES_NOT_ALLOWED =
      "Nodes %s and %s are already connected by a different edge. To construct a graph "

 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */
final class EdgesConnecting<E> extends AbstractSet<E> {

  private final Map<?, E> nodeToOutEdge;
  private final Object targetNode;

  EdgesConnecting(Map<?, E> nodeToEdgeMap, Object targetNode) {
    this.nodeToOutEdge = checkNotNull(nodeToEdgeMap);
    this.targetNode = checkNotNull(targetNode);
  }

 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */
final class EdgesConnecting<E> extends AbstractSet<E> {

  private final Map<?, E> nodeToOutEdge;
  private final Object targetNode;

  EdgesConnecting(Map<?, E> nodeToEdgeMap, Object targetNode) {
    this.nodeToOutEdge = checkNotNull(nodeToEdgeMap);
    this.targetNode = checkNotNull(targetNode);
  }

  }

  @Override
  public Set<N> adjacentNodes() {
    return Collections.unmodifiableSet(((BiMap<E, N>) incidentEdgeMap).values());
  }

  @Override
  public Set<E> edgesConnecting(N node) {
    return new EdgesConnecting<>(((BiMap<E, N>) incidentEdgeMap).inverse(), node);
  }

      adjacentNodes = HashMultiset.create(incidentEdgeMap.values());
      adjacentNodesReference = new SoftReference<>(adjacentNodes);
    }
    return adjacentNodes;
  }

  @Override
  public Set<E> edgesConnecting(N node) {
    return new MultiEdgesConnecting<E>(incidentEdgeMap, node) {
      @Override
      public int size() {
        return adjacentNodesMultiset().count(node);
      }
    };
  }

  @Override