∀ {X Y Z : AlgebraicGeometry.Scheme} (f : X ⟶ Y) (g : Y ⟶ Z) [inst : AlgebraicGeometry.IsOpenImmersion f]
  [inst_1 : AlgebraicGeometry.IsOpenImmersion g] (U : X.Opens),
  AlgebraicGeometry.Scheme.Hom.appIso (CategoryTheory.CategoryStruct.comp f g) U =
    CategoryTheory.Functor.mapIso Z.presheaf (CategoryTheory.eqToIso ⋯).op ≪≫
      AlgebraicGeometry.Scheme.Hom.appIso g ((AlgebraicGeometry.Scheme.Hom.opensFunctor f).obj U) ≪≫
        AlgebraicGeometry.Scheme.Hom.appIso f U