∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {sq₁ sq₂ : CategoryTheory.Square C} (self : sq₁.Hom sq₂),
  CategoryTheory.CategoryStruct.comp sq₁.f₃₄ self.τ₄ = CategoryTheory.CategoryStruct.comp self.τ₃ sq₂.f₃₄