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