undirectedGraph.addNode(node4);
undirectedGraph.addNode(node5);
undirectedGraph.addNode(node6);
undirectedGraph.addNode(node7);
undirectedGraph.addNode(node8);
undirectedGraph.addNode(node9);
Edge edge12 = graphModel.factory().newEdge(node1, node2, false);
Edge edge23 = graphModel.factory().newEdge(node2, node3, false);
Edge edge45 = graphModel.factory().newEdge(node4, node5, false);
Edge edge56 = graphModel.factory().newEdge(node5, node6, false);
Edge edge64 = graphModel.factory().newEdge(node6, node4, false);