proposition: Lemma gacent_gen A : A \subset D -> 'C_(|to)(<<A>>) = 'C_(|to)(A).
proof: Proof. by move=> sAD; rewrite /gacent ![D :&: _](setIidPr _) ?gen_subG ?afix_gen_in. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)