∀ {α : Type u} {cmp : α → α → Ordering} {t : Std.DTreeMap.Raw α (fun x => Unit) cmp} [Std.TransCmp cmp]
  [inst : Inhabited α],
  t.WF → ∀ {l : List α} {k : α}, k ∈ t → (Std.DTreeMap.Raw.Const.insertManyIfNewUnit t l).getKey! k = t.getKey! k