proposition: Lemma prefreeg_uniq rD : uniq [seq zx.2 | zx <- rD].
proof: Proof. exact/reduced_uniq/prefreeg_reduced. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)