∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [inst_1 : CategoryTheory.Category.{v₂, u₂} D]
  (F : CategoryTheory.Functor C D) {I : Type u_1} (X : I → C) (Y : C),
  CategoryTheory.Sieve.functorPushforward F (CategoryTheory.Sieve.ofObjects X Y) ≤
    CategoryTheory.Sieve.ofObjects (F.obj ∘ X) (F.obj Y)