proposition: Lemma subitv_refl : reflexive subitv.
proof: Proof. by case=> /= ? ?; rewrite !lexx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)