proposition: Lemma tperm2 x y : tperm x y * tperm x y = 1.
proof: Proof. by rewrite -{1}tpermV mulVg. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)