proposition: Lemma homoW : {homo f : x y / aR' x y >-> rR' x y} -> {homo f : x y / aR x y >-> rR x y}.
proof: Proof. by move=> mf ???; apply: (@homoW_in D D) => // ????; apply: mf. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool)