proposition: Lemma fgmulg1 : right_id fgone fgmul.
proof: Proof. move=> g; rewrite fgmulgU [RHS]monalgE. by apply/eq_bigr=> k _; rewrite mulr1 mulm1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap