proposition: Lemma remove_edges_vertexK (G : pre_graph) E z : E `<=` edges_at G z -> (G - E) \ z ≡G G \ z.
proof: Proof. move => EIz. split => //=. by rewrite fsetDDl edges_at_remove_edges fsetUDl fsetDv fsetD0 (fsetUidPr _ _ EIz). 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)