fact: Definition is_epi := forall (P : {fpmod R}) (psi : 'Mor(N, P)), phi ** psi %= 0 -> psi %= 0.
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