proposition: Lemma remove_vertexC (G : pre_graph) (x y : VT) : (G \ x \ y)%O = (G \ y \ x)%O.
proof: Proof. rewrite /remove_vertex/=; f_equal. - by rewrite fsetDDl fsetUC -fsetDDl. - by rewrite !edges_at_del fsetDDD fsetUC -fsetDDD. Qed.
imports: HB(structures) Coq(Relation_Definitions Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom rewriting) GraphTheory(finmap_plus)