∀ {T : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} T] {X : T} {A B : CategoryTheory.Over X} (f : A ⟶ B) {Z : T}
  (h : (CategoryTheory.Functor.fromPUnit X).obj B.right ⟶ Z),
  CategoryTheory.CategoryStruct.comp f.left (CategoryTheory.CategoryStruct.comp B.hom h) =
    CategoryTheory.CategoryStruct.comp A.hom h