proposition: Lemma valid_path_tail: forall g p, valid_path g p -> valid_path g (ptail g p).
proof: Proof. intros. destruct p as [v p]. destruct p; unfold ptail; auto. apply valid_path_cons with v; auto. Qed.
imports: Coq.Logic.ProofIrrelevance Coq.micromega.Lia CertiGraph.lib.Coqlib CertiGraph.lib.EnumEnsembles CertiGraph.lib.List_ext CertiGraph.lib.EquivDec_ext CertiGraph.graph.graph_model Coq.Lists.List Coq.Lists.ListDec