∀ {α : Type u_1} {β : α → Type u_2} (sz : ℕ) (k' : α) (v' : β k') (l' r' : Std.DTreeMap.Internal.Impl α β),
  (Std.DTreeMap.Internal.Impl.inner sz k' v' l' r').Balanced →
    ∀ (d : Std.DTreeMap.Internal.Impl α β),
      l'.size - 1 ≤ d.size →
        d.size ≤ l'.size + 1 →
          Std.DTreeMap.Internal.Impl.BalanceLErasePrecond d.size r'.size ∨
            Std.DTreeMap.Internal.Impl.BalanceLErasePrecond r'.size d.size