proposition: Lemma predeg_cons D k x : predeg ((k, x) :: D) = k + predeg D.
proof: Proof. by rewrite /predeg big_cons. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)