∀ {α : Type u} {β : Type v} {t : Std.DTreeMap.Internal.Impl α fun x => β},
  t.Balanced →
    ∀ {i : ℕ}, Std.DTreeMap.Internal.Impl.Const.entryAtIdx? t i = Option.map (fun x => (x.fst, x.snd)) t.toListModel[i]?