∀ {X : AlgebraicGeometry.Scheme} (U : X.Opens) {V : (↑U).Opens} (x : ↥U) (hx : x ∈ V) {Z : CommRingCat}
  (h : X.presheaf.stalk ↑x ⟶ Z),
  CategoryTheory.CategoryStruct.comp ((↑U).presheaf.germ V x hx)
      (CategoryTheory.CategoryStruct.comp (U.stalkIso x).hom h) =
    CategoryTheory.CategoryStruct.comp (X.presheaf.germ ((AlgebraicGeometry.Scheme.Hom.opensFunctor U.ι).obj V) ↑x ⋯) h