∀ {α : Type u} {β : Type v} {γ : Type w} {β' : Type v'} (s₁ : Stream'.Seq α) (s₂ : Stream'.Seq β) (f : β → β')
  (g : α → β' → γ), Stream'.Seq.zipWith g s₁ (Stream'.Seq.map f s₂) = Stream'.Seq.zipWith (fun a b => g a (f b)) s₁ s₂