proposition: Lemma add_vlabel_mon0 G x: G [tst x <- 1] ≃ G.
proof: Proof. Iso bij_id bij_id xpred0. split=>//=. move=>v. case eq_op=>//. by rewrite monC monU. Defined.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)