proposition: Lemma oiso2_oarc (F G : pre_graph) (i : F ⩭2 G) e x y u : oarc F e x u y -> oarc G (efun_of i e) (i x) u (i y).
proof: Proof. case => Ee [b] [A B C]. split; first exact: im_efun_of. exists (edir_of i e (+) b). rewrite !oiso2_endpoint // -addbN !addbA !addbb !addFb A B. split => //. exact: eqvb_trans (oiso2_le _ _ ) _. Qed.
imports: Coq(Relation_Definitions Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph mgraph2) GraphTheory(rewriting open_confluence finmap_plus)