proposition: Lemma dprodg1 : right_id 1 dprod.
proof: Proof. by move=> A; rewrite /dprod subsetIr cprodg1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)