∀ {C₁ : Type u_1} {C₂ : Type u_2} [inst : CategoryTheory.Category.{v_1, u_1} C₁]
  [inst_1 : CategoryTheory.Category.{v_2, u_2} C₂] {G : CategoryTheory.Functor C₁ C₂} {F : CategoryTheory.Functor C₂ C₁}
  [F.Full] [F.Faithful] (adj : G ⊣ F),
  ((CategoryTheory.MorphismProperty.isomorphisms C₂).inverseImage G).functorCategory C₁ adj.unit