return delegate().hasEdgeConnecting(endpoints);
  }

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

  @Override
  public Optional<V> edgeValue(EndpointPair<N> endpoints) {
    return delegate().edgeValue(endpoints);
  }

  @Override
  public @Nullable V edgeValueOrDefault(N nodeU, N nodeV, @Nullable V defaultValue) {

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

    @Override
    public Optional<V> edgeValue(N nodeU, N nodeV) {
      return delegate().edgeValue(nodeV, nodeU); // transpose
    }

    @Override
    public Optional<V> edgeValue(EndpointPair<N> endpoints) {
      return delegate().edgeValue(transpose(endpoints));
    }

    @Override