∀ {U : TopCat} (X : AlgebraicGeometry.LocallyRingedSpace) {f : U ⟶ X.toTopCat}
  (h : Topology.IsOpenEmbedding ⇑(CategoryTheory.ConcreteCategory.hom f)) (x : ↑U),
  CategoryTheory.IsIso (AlgebraicGeometry.LocallyRingedSpace.Hom.stalkMap (X.ofRestrict h) x)