proposition: Lemma impI (T : System) (f g : Formula): SysPrf (Ensembles.Add T g) f -> SysPrf T (g -> f)%fol.
proof: Proof. intros ?; now apply (DeductionTheorem L). Qed.
imports: Coq(Ensembles List) hydras.Ackermann(ListExt folProof folProp Deduction)