proposition: Lemma isog_pgroup pi : G \isog H -> pi.-group G = pi.-group H.
proof: Proof. by move=> isoGH; rewrite /pgroup (card_isog isoGH). Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)