∀ {𝒮 : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} 𝒮] {𝒳 : CategoryTheory.BasedCategory 𝒮}
  {𝒴 : CategoryTheory.BasedCategory 𝒮} {F G : CategoryTheory.BasedFunctor 𝒳 𝒴} (α : F ⟶ G) [CategoryTheory.IsIso α],
  CategoryTheory.IsIso α.toNatTrans