proposition: Lemma lker0_compVf f : lker f == 0%VS -> (f^-1 \o f = \1)%VF.
proof: Proof. by move/lker0_lfunK=> fK; apply/lfunP=> u; rewrite !lfunE /= fK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)