proposition: Lemma adj_edge_vvalid: forall g e u v, adj_edge g e u v -> vvalid g u /\ vvalid g v.
proof: Proof. intros. destruct H. destruct H as [? [? ?]]. destruct H0; destruct H0. all: subst u; subst v; split; auto. Qed.
imports: Coq.Logic.Classical CertiGraph.lib.List_ext CertiGraph.lib.EquivDec_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_relation CertiGraph.graph.path_lemmas CertiGraph.graph.graph_gen CertiGraph.graph.FiniteGraph