proposition: Lemma remove_edgesK (G : pre_graph) E z : E `<=` edges_at G z -> (remove_edges G E) \ z ≡G G \ z.
proof: Proof. move => subE. split => //=. by rewrite edges_at_remove_edges fsetDDD (fsetUidPr _ _ subE). 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)