proposition: Lemma comm_mx1 f : comm_mx f 1%:M.
proof: Proof. by rewrite /comm_mx mulmx1 mul1mx. 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)