directedGraph.addNode(node3);
directedGraph.addNode(node4);
directedGraph.addNode(node5);
directedGraph.addNode(node6);
directedGraph.addNode(node7);
directedGraph.addNode(node8);
Edge edge12 = graphModel.factory().newEdge(node1, node2);
Edge edge23 = graphModel.factory().newEdge(node2, node3);
Edge edge34 = graphModel.factory().newEdge(node3, node4);
Edge edge41 = graphModel.factory().newEdge(node4, node1);
Edge edge56 = graphModel.factory().newEdge(node5, node6);