∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} [inst : TopologicalSpace α] [inst_1 : TopologicalSpace β]
  [inst_2 : TopologicalSpace γ] {f : α → β} {s : Set α} {x : α} {g : β → γ} {t : Set β},
  ContinuousWithinAt g t (f x) → ContinuousWithinAt f s x → Set.MapsTo f s t → ContinuousWithinAt (g ∘ f) s x