public function createGraph()
    {
        $newgraph = $this->graph->createGraphCloneEdgeless();

        foreach ($this->graph->getEdges() as $edge) {
            if (!($edge instanceof EdgeDirected)) {
                throw new UnexpectedValueException('Edge is undirected');
            }
            $newgraph->createEdgeCloneInverted($edge);
        }

        return $newgraph;
    }