∀ {α : Type u} {β : Type v} {γ δ : Type w} {cmp : α → α → Ordering} {t : Std.TreeMap α β cmp} {f : α → β → γ}
  {g : α → γ → δ}, (Std.TreeMap.map g (Std.TreeMap.map f t)).Equiv (Std.TreeMap.map (fun k v => g k (f k v)) t)