∀ {X Y U : AlgebraicGeometry.Scheme} (f : U ⟶ X) (g : X ⟶ Y) [inst : AlgebraicGeometry.IsOpenImmersion f]
  [inst_1 : AlgebraicGeometry.LocallyOfFinitePresentation g],
  (TopologicalSpace.Opens.map f.base).obj (AlgebraicGeometry.Scheme.Hom.smoothLocus g) =
    AlgebraicGeometry.Scheme.Hom.smoothLocus (CategoryTheory.CategoryStruct.comp f g)