proposition: Lemma lift_perm_id i j s : lift_perm i j s i = j.
proof: Proof. by rewrite permE /lift_perm_fun unlift_none. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)