fact: Definition addmor phi1 phi2 : 'Mor(M, N) := Morphism (addmor_proof phi1 phi2).
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