proposition: Lemma lcoset_trans x y z : x \in y *: G -> y \in z *: G -> x \in z *: G.
proof: Proof. by move/lcoset_transl->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)