proposition: Lemma permut_tactic_setup : forall C l1 l2, C (\{} \u l1 \u \{}) (l2 \u \{}) -> C l1 l2.
proof: Proof. Proof using. intros. rews_permut_simpl. eauto. Qed.
imports: TLC(LibTactics LibLogic LibReflect LibRelation LibList LibInt LibNat LibOperation LibEpsilon LibSet LibMonoid)