proposition: Lemma trivIset1 : trivIset [set x].
proof: Proof. apply/trivIsetP => A B. rewrite !inE => /eqP -> /eqP ->. by rewrite eqxx. Qed.
imports: mathcomp(all_ssreflect ssralg fingroup zmodp poly ssrnum) mathcomp(matrix perm) ssr_ext ssralg_ext fdist