import Adam.Metadata


-- -- INCORPORATED
-- example (A  B : Prop) : (A → B) ↔ (¬ B → ¬A) := by
--   constructor
--   intro h nb
--   by_contra
--   have : B
--   apply h
--   assumption
--   contradiction
--   intro h a
--   by_contra
--   have : ¬ A
--   apply h
--   assumption
--   contradiction
