proposition: Lemma fmmulm1 : right_id fmone fmmul.
proof: Proof. by move=> m; rewrite !fmE cats0 fmK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap