Edge edge67 = graphModel.factory().newEdge(node6, node7, false);
Edge edge78 = graphModel.factory().newEdge(node7, node8, false);
Edge edge81 = graphModel.factory().newEdge(node8, node1, false);
Edge edge14 = graphModel.factory().newEdge(node1, node4, false);
Edge edge85 = graphModel.factory().newEdge(node8, node5, false);
undirectedGraph.addEdge(edge12);
undirectedGraph.addEdge(edge23);
undirectedGraph.addEdge(edge34);
undirectedGraph.addEdge(edge45);
undirectedGraph.addEdge(edge56);
undirectedGraph.addEdge(edge67);