proposition: Lemma merge_mergeE x: merge_merge (\pi (\pi x)) = \pi x.
proof: Proof. apply quot_quotE. Qed.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)