∀ {X : AlgebraicGeometry.PresheafedSpace CommRingCat} (Y : AlgebraicGeometry.Scheme) (f : X ⟶ Y.toPresheafedSpace)
  [H : AlgebraicGeometry.PresheafedSpace.IsOpenImmersion f],
  (AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.toSchemeHom Y f).toPshHom = f