proposition: Lemma adjacent_last_adjacent: forall g u v, adjacent_last g (Some u) v <-> adjacent g u v.
proof: Proof. intros; split; intros; destruct H; exists x; apply H. 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