directedGraph.addNode(node1);
directedGraph.addNode(node2);
directedGraph.addNode(node3);
directedGraph.addNode(node4);
directedGraph.addNode(node5);
directedGraph.addNode(node6);
Edge edge21 = graphModel.factory().newEdge(node2, node1);
Edge edge31 = graphModel.factory().newEdge(node3, node1);
Edge edge41 = graphModel.factory().newEdge(node4, node1);
Edge edge51 = graphModel.factory().newEdge(node5, node1);