{α : Type u} →
  {β : Type v} →
    {motive : (α ≃. β) → Sort u_1} →
      (t : α ≃. β) →
        ((toFun : α → Option β) →
            (invFun : β → Option α) →
              (inv : ∀ (a : α) (b : β), invFun b = some a ↔ toFun a = some b) →
                motive { toFun := toFun, invFun := invFun, inv := inv }) →
          motive t