{α : Type u_1} →
  {β : Type u_2} →
    (l' : Std.DTreeMap.Internal.Impl α fun x => β) →
      (motive : Std.DTreeMap.Internal.Impl.SizedBalancedTree α (fun x => β) (l'.size - 1) (l'.size + 1) → Sort u_3) →
        (x : Std.DTreeMap.Internal.Impl.SizedBalancedTree α (fun x => β) (l'.size - 1) (l'.size + 1)) →
          ((d : Std.DTreeMap.Internal.Impl α fun x => β) →
              (hd : d.Balanced) →
                (hd'₁ : l'.size - 1 ≤ d.size) →
                  (hd'₂ : d.size ≤ l'.size + 1) →
                    motive { impl := d, balanced_impl := hd, lb_le_size_impl := hd'₁, size_impl_le_ub := hd'₂ }) →
            motive x