∀ {X Y Z : AlgebraicGeometry.LocallyRingedSpace} (f : X ⟶ Z) (g : Y ⟶ Z)
  [H : AlgebraicGeometry.LocallyRingedSpace.IsOpenImmersion f] (x : ↑↑(Y.restrict ⋯).toPresheafedSpace),
  IsLocalHom
    (CommRingCat.Hom.hom
      (AlgebraicGeometry.PresheafedSpace.Hom.stalkMap
        (AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.pullbackConeOfLeftFst f.toHom g.toHom) x))