proposition: Lemma pseries_sub pis : GFunctor.closed (@pseries pis).
proof: Proof. by case: (pseries_subfun pis). 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)