∀ {X Y Z : AlgebraicGeometry.Scheme} (f : X ⟶ Y) (g : Y ⟶ Z) [AlgebraicGeometry.IsAffineHom f]
  [AlgebraicGeometry.IsAffineHom g], AlgebraicGeometry.IsAffineHom (CategoryTheory.CategoryStruct.comp f g)