proposition: Lemma tpermKg x y : involutive (mulg (tperm x y)).
proof: Proof. by move=> s; apply/permP=> z; rewrite !permM tpermK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)