proposition: Lemma qisom_ker_proof : 'ker (coset G) \subset 'ker (coset H).
proof: Proof. by rewrite eqGH. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)