∀ (𝕜 : Type u_1) [inst : NontriviallyNormedField 𝕜] {E : Type u_2} [inst_1 : SeminormedAddCommGroup E]
  [inst_2 : NormedSpace 𝕜 E] [ProperSpace 𝕜] (x' : StrongDual 𝕜 E) (r : ℝ),
  IsCompact (⇑WeakDual.toStrongDual ⁻¹' Metric.closedBall x' r)