proposition: Lemma NOABT_singleton_primary : forall A out, no_output_at_backup_trace [(Primary, @inr A _ out)].
proof: Proof. Proof using. unfold no_output_at_backup_trace, no_output_at_backup. simpl. intuition. subst. simpl in *. find_inversion. auto. Qed.
imports: Verdi(Verdi HandlerMonad)