proposition: Lemma Fid3 : 'Fix_to_g[1] = setT.
proof: Proof. by apply/setP=> x /=; rewrite (sameP afix1P eqP) !inE act1 eqxx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop finset fingroup) mathcomp(action perm primitive_action)