proposition: Lemma tperm1 x : tperm x x = 1.
proof: Proof. by apply/permP => z; rewrite perm1; case: tpermP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)