Node node2 = graphModel.factory().newNode("1");
Node node3 = graphModel.factory().newNode("2");
undirectedGraph.addNode(node1);
undirectedGraph.addNode(node2);
undirectedGraph.addNode(node3);
Edge edge11 = graphModel.factory().newEdge(node1, node1, false);
Edge edge12 = graphModel.factory().newEdge(node1, node2, false);
Edge edge23 = graphModel.factory().newEdge(node2, node3, false);
Edge edge33 = graphModel.factory().newEdge(node3, node3, false);