proposition: Corollary connected_symm: forall g u v, connected g u v -> connected g v u.
proof: Proof. intros. destruct H as [p ?]. exists (rev p). apply connected_by_path_rev; 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