proposition: Lemma group_setJ A x : group_set (A :^ x) = group_set A.
proof: Proof. by rewrite /group_set mem_conjg conj1g -conjsMg conjSg. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)