∀ {K : CategoryTheory.Precoverage AlgebraicGeometry.Scheme} [AlgebraicGeometry.Scheme.JointlySurjective K]
  {X : AlgebraicGeometry.Scheme} (𝒰 : AlgebraicGeometry.Scheme.Cover K X), ⋃ i, Set.range ⇑(𝒰.f i) = Set.univ