proposition: Lemma agenv_id U : agenv (agenv U) = agenv U.
proof: Proof. apply/eqP; rewrite eqEsubv sub_agenv andbT. by rewrite agenv_sub_modl ?sub1_agenv ?agenvM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype div tuple finfun bigop ssralg) mathcomp(finalg zmodp matrix vector poly)