∀ {C₁ : Type u_6} {C₂ : Type u_2} {C₃ : Type u_4} [inst : CategoryTheory.Category.{u_5, u_6} C₁]
  [inst_1 : CategoryTheory.Category.{u_1, u_2} C₂] [inst_2 : CategoryTheory.Category.{u_3, u_4} C₃]
  {G : CategoryTheory.Functor C₁ᵒᵖ (CategoryTheory.Functor C₃ C₂)} {f₁ : CategoryTheory.Arrow C₁}
  {f₃ f₃' : CategoryTheory.Arrow C₃} (sq₁₃ : G.PullbackObjObj f₁.hom f₃.hom) (sq : f₃ ⟶ f₃'),
  CategoryTheory.CategoryStruct.comp
      (CategoryTheory.CategoryStruct.comp sq₁₃.fst
        ((G.obj (Opposite.op f₁.left)).map (CategoryTheory.Arrow.Hom.left sq)))
      ((G.obj (Opposite.op f₁.left)).map f₃'.hom) =
    CategoryTheory.CategoryStruct.comp
      (CategoryTheory.CategoryStruct.comp sq₁₃.snd
        ((G.obj (Opposite.op f₁.right)).map (CategoryTheory.Arrow.Hom.right sq)))
      ((G.map f₁.hom.op).app f₃'.right)