Sort u_1 →
  {α : Type u} →
    {β : α → Type v} →
      {size : ℕ} →
        Std.DTreeMap.Internal.Impl.View α β size →
          {α' : Type u} → {β' : α' → Type v} → {size' : ℕ} → Std.DTreeMap.Internal.Impl.View α' β' size' → Sort u_1