proposition: Lemma im_permV s S : s^-1 @: S = s @^-1: S.
proof: Proof. exact: can2_imset_pre (permKV s) (permK s). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)