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);
Edge edge75 = graphModel.factory().newEdge(node7, node5, false);
undirectedGraph.addEdge(edge12);
undirectedGraph.addEdge(edge23);
undirectedGraph.addEdge(edge45);
undirectedGraph.addEdge(edge56);
undirectedGraph.addEdge(edge64);
undirectedGraph.addEdge(edge75);