∀ {X Y : AlgebraicGeometry.Scheme} (f : X ⟶ Y) [AlgebraicGeometry.Flat f] [AlgebraicGeometry.Surjective f]
  [AlgebraicGeometry.QuasiCompact f],
  CategoryTheory.Presieve.singleton f ∈ AlgebraicGeometry.Scheme.fpqcPrecoverage.coverings Y