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