∀ {m₁ : Type u_1 → Type u_2} {m₂ : Type u_3 → Type u_4} {α₁ r₁ : Type u_1} {α₂ r₂ : Type u_3} (F : m₁ r₁ ≃ m₂ r₂)
  (G : α₁ ≃ α₂) (f : ContT r₁ m₁ α₁),
  (fun f r => F.symm (f fun x => F (r (G.symm x)))) ((fun f r => F (f fun x => F.symm (r (G x)))) f) = f