∀ {α : Type u} {β : α → Type v} {cmp : α → α → Ordering} {t : Std.DTreeMap.Raw α β cmp} [Std.TransCmp cmp]
  [inst : Std.LawfulEqCmp cmp],
  t.WF →
    ∀ {k k' : α} {f : Option (β k) → Option (β k)}, ¬cmp k k' = Ordering.eq → (t.alter k f).contains k' = t.contains k'