∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X : AlgebraicGeometry.PresheafedSpace C}
  (Y : AlgebraicGeometry.SheafedSpace C) (f : X ⟶ Y.toPresheafedSpace)
  [H : AlgebraicGeometry.PresheafedSpace.IsOpenImmersion f],
  (AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.toSheafedSpaceHom Y f).hom.base = f.base