Edge edge12 = graphModel.factory().newEdge(node1, node2, false);
Edge edge13 = graphModel.factory().newEdge(node1, node3, false);
Edge edge14 = graphModel.factory().newEdge(node1, node4, false);
Edge edge15 = graphModel.factory().newEdge(node1, node5, false);
Edge edge16 = graphModel.factory().newEdge(node1, node6, false);
Edge edge27 = graphModel.factory().newEdge(node2, node7, false);
Edge edge37 = graphModel.factory().newEdge(node3, node7, false);
Edge edge47 = graphModel.factory().newEdge(node4, node7, false);
Edge edge57 = graphModel.factory().newEdge(node5, node7, false);
Edge edge67 = graphModel.factory().newEdge(node6, node7, false);
undirectedGraph.addEdge(edge12);