∀ {α : Type u} {β : Type v} {cmp : α → α → Ordering} {t : Std.TreeMap.Raw α β cmp} [Std.TransCmp cmp]
  [inst : Inhabited α],
  t.WF →
    ∀ {l : List (α × β)} {k k' : α},
      cmp k k' = Ordering.eq →
        List.Pairwise (fun a b => ¬cmp a.1 b.1 = Ordering.eq) l →
          k ∈ List.map Prod.fst l → (t.insertMany l).getKey! k' = k