directedGraph.addNode(node1);
directedGraph.addNode(node2);
directedGraph.addNode(node3);
directedGraph.addNode(node4);
directedGraph.addNode(node5);
directedGraph.addNode(node6);
Edge edge15 = graphModel.factory().newEdge(node1, node5);
Edge edge25 = graphModel.factory().newEdge(node2, node5);
Edge edge35 = graphModel.factory().newEdge(node3, node5);
Edge edge45 = graphModel.factory().newEdge(node4, node5);