proposition: Lemma gFcomp_closed : GFunctor.closed (F1 \o F2).
proof: Proof. by move=> gT G; rewrite !gFsub_trans. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat fintype) mathcomp(bigop finset fingroup morphism automorphism) mathcomp(quotient gproduct)