∀ {X Y Z : AlgebraicGeometry.Scheme} (f : X ⟶ Y) (g : Y ⟶ Z) [inst : AlgebraicGeometry.IsOpenImmersion f]
  [inst_1 : AlgebraicGeometry.IsOpenImmersion g] {X_1 Y_1 : X.Opens} (f_1 : X_1 ⟶ Y_1),
  CategoryTheory.CategoryStruct.comp
      (((AlgebraicGeometry.Scheme.Hom.opensFunctor f).comp (AlgebraicGeometry.Scheme.Hom.opensFunctor g)).map f_1)
      ((fun x => CategoryTheory.eqToIso ⋯) Y_1).hom =
    CategoryTheory.CategoryStruct.comp ((fun x => CategoryTheory.eqToIso ⋯) X_1).hom
      ((AlgebraicGeometry.Scheme.Hom.opensFunctor (CategoryTheory.CategoryStruct.comp f g)).map f_1)