∀ {X Y Z : AlgebraicGeometry.Scheme} (f : X ⟶ Z) (g : Y ⟶ Z) [inst : AlgebraicGeometry.IsClosedImmersion f]
  (H : AlgebraicGeometry.Scheme.Hom.ker f ≤ AlgebraicGeometry.Scheme.Hom.ker g) {Z_1 : AlgebraicGeometry.Scheme}
  (h : Z ⟶ Z_1),
  CategoryTheory.CategoryStruct.comp (AlgebraicGeometry.IsClosedImmersion.lift f g H)
      (CategoryTheory.CategoryStruct.comp f h) =
    CategoryTheory.CategoryStruct.comp g h