∀ {E : Type u_1} {ι : Type u_2} [inst : NormedAddCommGroup E] [inst_1 : NormedSpace ℂ E] {K : Set ℂ} {δ : ℝ}
  {φ : Filter ι} {F : ι → ℂ → E} {f : ℂ → E},
  TendstoUniformlyOn F f φ (Metric.cthickening δ K) →
    0 < δ →
      (∀ᶠ (n : ι) in φ, ContinuousOn (F n) (Metric.cthickening δ K)) →
        TendstoUniformlyOn (Complex.cderiv δ ∘ F) (Complex.cderiv δ f) φ K