proposition: Lemma directv_trivial U : directv (unwrap (@trivial_addv U)).
proof: Proof. exact: eqxx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)