∀ {A : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} A] {B : Type u_2}
  [inst_1 : CategoryTheory.Category.{v_2, u_2} B] {T : Type u_3} [inst_2 : CategoryTheory.Category.{v_3, u_3} T]
  {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {P : CategoryTheory.MorphismProperty T}
  {Q : CategoryTheory.MorphismProperty A} {W : CategoryTheory.MorphismProperty B} [inst_3 : Q.IsMultiplicative]
  [inst_4 : W.IsMultiplicative] {X Y Z : CategoryTheory.MorphismProperty.Comma L R P Q W} (f : X ⟶ Y) (g : Y ⟶ Z)
  {Z_1 : A} (h : Z.left ⟶ Z_1),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.CategoryStruct.comp f g).left h =
    CategoryTheory.CategoryStruct.comp f.left (CategoryTheory.CategoryStruct.comp g.left h)