Edge edge12 = graphModel.factory().newEdge(node1, node2);
Edge edge14 = graphModel.factory().newEdge(node1, node4);
Edge edge23 = graphModel.factory().newEdge(node2, node3);
Edge edge25 = graphModel.factory().newEdge(node2, node5);
Edge edge35 = graphModel.factory().newEdge(node3, node5);
Edge edge43 = graphModel.factory().newEdge(node4, node3);
Edge edge51 = graphModel.factory().newEdge(node5, node1);
Edge edge54 = graphModel.factory().newEdge(node5, node4);
directedGraph.addEdge(edge12);
directedGraph.addEdge(edge14);
directedGraph.addEdge(edge23);