return AbstractValueGraph.this.edges();
      }

      @Override
      public boolean isDirected() {
        return AbstractValueGraph.this.isDirected();
      }

      @Override
      public boolean allowsSelfLoops() {
        return AbstractValueGraph.this.allowsSelfLoops();
      }

      @Override
      public ElementOrder<N> nodeOrder() {
        return AbstractValueGraph.this.nodeOrder();
      }

 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 */
abstract class ForwardingValueGraph<N, V> extends AbstractValueGraph<N, V> {

  abstract ValueGraph<N, V> delegate();

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

  /**
   * Defer to {@link AbstractValueGraph#edges()} (based on {@link #successors(Object)}) for full
   * edges() implementation.
   */
  @Override

 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 */
abstract class ForwardingValueGraph<N, V> extends AbstractValueGraph<N, V> {

  abstract ValueGraph<N, V> delegate();

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

  /**
   * Defer to {@link AbstractValueGraph#edges()} (based on {@link #successors(Object)}) for full
   * edges() implementation.
   */
  @Override

      return delegate().hasEdgeConnecting(transpose(endpoints));
    }
  }

  // NOTE: this should work as long as the delegate graph's implementation of edges() (like that of
  // AbstractValueGraph) derives its behavior from calling successors().
  private static final class TransposedValueGraph<N, V> extends ForwardingValueGraph<N, V> {
    private final ValueGraph<N, V> graph;

      return delegate().hasEdgeConnecting(transpose(endpoints));
    }
  }

  // NOTE: this should work as long as the delegate graph's implementation of edges() (like that of
  // AbstractValueGraph) derives its behavior from calling successors().
  private static final class TransposedValueGraph<N, V> extends ForwardingValueGraph<N, V> {
    private final ValueGraph<N, V> graph;