proposition: Lemma coeffU k x y : coeff y << k *g x >> = k * (x == y)%:R.
proof: Proof. by rewrite /coeff liftU. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)