∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [inst_1 : CategoryTheory.Category.{v₂, u₂} D]
  (self : CategoryTheory.Functor C D) {X Y Z : C} (f : X ⟶ Y) (g : Y ⟶ Z),
  CategoryTheory.CategoryStruct.comp (self.map f) (self.map g) = self.map (CategoryTheory.CategoryStruct.comp f g)