∀ {C : Type u_4} [inst : CategoryTheory.Category.{u_3, u_4} C] {D : Type u_2}
  [inst_1 : CategoryTheory.Category.{u_1, u_2} D] (sq : CategoryTheory.Square C) (F : CategoryTheory.Functor C D),
  CategoryTheory.CategoryStruct.comp (F.map sq.f₁₂) (F.map sq.f₂₄) =
    CategoryTheory.CategoryStruct.comp (F.map sq.f₁₃) (F.map sq.f₃₄)