∀ {X : Type u_1} {Y : Type u_2} [inst : TopologicalSpace X] [inst_1 : TopologicalSpace Y] [T1Space X] {x : X}
  {s t : Set X} {f : X → Y} (y : X), s =ᶠ[nhdsWithin x {y}ᶜ] t → (ContinuousWithinAt f s x ↔ ContinuousWithinAt f t x)