∀ {α : Type u} {instOrd : Ord α} {t : Std.DTreeMap.Internal.Impl α fun x => Unit} [Std.TransOrd α] [inst : Inhabited α]
  (h : t.WF) {l : List α} {k k' : α},
  compare k k' = Ordering.eq →
    k ∉ t →
      List.Pairwise (fun a b => ¬compare a b = Ordering.eq) l →
        k ∈ l → (↑(Std.DTreeMap.Internal.Impl.Const.insertManyIfNewUnit t l ⋯)).getKey! k' = k