proposition: Lemma merge_nothing'E x: merge_nothing' (\pi x) = x.
proof: Proof. by rewrite /=merge_surjE. Qed.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)