proposition: Lemma lift_subproof (M N L : {fpmod R}) (phi : 'Mor(M,N)) (psi : 'Mor(N,L)) : phi ** psi %= 0 -> pres L %| pres (quot_by phi) *m psi.
proof: Proof. by rewrite /eqmor subr0 /= mul_col_mx dvd_mx_col dvdmx_morphism. 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