proposition: Lemma merge_merge: merge (merge F e) e' ≃ merge F (equiv_comp e').
proof: Proof. eexists. eapply hom_merge_merge. Defined.
imports: Coq(Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij) GraphTheory(equiv digraph setoid_bigop structures)