{α : Type u_1} →
  {β : α → Type u_2} →
    (l : Std.DTreeMap.Internal.Impl α β) →
      (motive : Std.DTreeMap.Internal.Impl.SizedBalancedTree α β (l.size - 1) (l.size + 1) → Sort u_3) →
        (x : Std.DTreeMap.Internal.Impl.SizedBalancedTree α β (l.size - 1) (l.size + 1)) →
          ((newL : Std.DTreeMap.Internal.Impl α β) →
              (h₁ : newL.Balanced) →
                (h₂ : l.size - 1 ≤ newL.size) →
                  (h₃ : newL.size ≤ l.size + 1) →
                    motive { impl := newL, balanced_impl := h₁, lb_le_size_impl := h₂, size_impl_le_ub := h₃ }) →
            motive x