proposition: Lemma morphism1_subproof x (X : 'M_(x, _)) : X %| pres N -> X %| pres N *m 1%:M.
proof: Proof. by rewrite mulmx1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements stronglydiscrete coherent edr