∀ {𝕜 : Type u_1} {E : Type u_3} [inst : NormedField 𝕜] [inst_1 : AddCommGroup E] [inst_2 : Module 𝕜 E]
  [inst_3 : TopologicalSpace E] [ContinuousSMul 𝕜 E] [ContinuousAdd E] {s t : Set E},
  Bornology.IsVonNBounded 𝕜 (s + t) ↔ s = ∅ ∨ t = ∅ ∨ Bornology.IsVonNBounded 𝕜 s ∧ Bornology.IsVonNBounded 𝕜 t