∀ {α : Type u} {cmp : α → α → Ordering} {t : Std.TreeMap.Raw α Unit cmp} [Std.TransCmp cmp],
  t.WF →
    ∀ {l : List α} {k k' : α},
      cmp k k' = Ordering.eq →
        k ∉ t →
          List.Pairwise (fun a b => ¬cmp a b = Ordering.eq) l → k ∈ l → (t.insertManyIfNewUnit l).getKey? k' = some k