proposition: Lemma subnormal_refl G : G <|<| G.
proof: Proof. by apply/subnormalP; exists [::]. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(fintype bigop finset fingroup morphism) mathcomp(automorphism quotient action commutator center)