proposition: Lemma left_valid (pg: PreGraph V E) {bi: BinGraph pg left_out_edge right_out_edge}: forall x, vvalid pg x -> evalid pg (left_out_edge x).
proof: Proof. intros. pose proof only_two_edges x (left_out_edge x). tauto. Qed.
imports: CertiGraph.lib.Coqlib CertiGraph.lib.Ensembles_ext CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.lib.relation_list CertiGraph.lib.Equivalence_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_gen CertiGraph.graph.MathGraph