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