∀ {C : Type u_3} [inst : CategoryTheory.Category.{u_2, u_3} C] {J : CategoryTheory.Precoverage C}
  {P : CategoryTheory.Functor Cᵒᵖ (Type u_1)},
  CategoryTheory.Presieve.IsSheaf J.toGrothendieck P →
    ∀ {S : C} {R : CategoryTheory.Presieve S}, R ∈ J.coverings S → CategoryTheory.Presieve.IsSheafFor P R