proposition: Lemma pprod1g : left_id 1 pprod.
proof: Proof. by move=> A; rewrite /pprod eqxx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)