proposition: Lemma memv_pick U : vpick U \in U.
proof: Proof. by rewrite mem_r2v nz_row_sub. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)