{α : Type u} →
  {β : α → Type v} →
    {size : ℕ} →
      {motive : Std.DTreeMap.Internal.Impl.Tree α β size → Sort u_1} →
        ((impl : Std.DTreeMap.Internal.Impl α β) →
            (balanced_impl : impl.Balanced) →
              (size_impl : impl.size = size) →
                motive { impl := impl, balanced_impl := balanced_impl, size_impl := size_impl }) →
          (t : Std.DTreeMap.Internal.Impl.Tree α β size) → motive t