proposition: Lemma norm_conj_autE : {in 'N(G) & G, forall x y, conj_aut x y = y ^ x}.
proof: Proof. by move=> x y nGx Gy; rewrite /= autE //= subgK. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat fintype) mathcomp(finset fingroup perm morphism)