fact: Definition epi_of phi (phi_epi : is_epi phi) := @Epimorphism phi (@introTF _ _ true (epiP phi) phi_epi).
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