proposition: Lemma col_colsub m n1 n2 (g : 'I_n2 -> 'I_n1) (A : 'M_(m, n1)) i : col i (colsub g A) = col (g i) A.
proof: Proof. by rewrite col_mxsub mxsub_id. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)