def add_edge(self, u, v, **attr):
        if u not in self.succ:
            self.succ[u] = self.adjlist_dict_factory()
            self.pred[u] = self.adjlist_dict_factory()
            self.node[u] = self.node_dict_factory()
        if v not in self.succ:
            self.succ[v] = self.adjlist_dict_factory()
            self.pred[v] = self.adjlist_dict_factory()
            self.node[v] = self.node_dict_factory()
        super(GraphSolver, self).add_edge(u, v, **attr)
dataset/ETHPy150Open openstack/fuel-web/nailgun/nailgun/orchestrator/orchestrator_graph.py/GraphSolver.add_edge/original