∀ {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 →
    ∀ (r' : Std.DTreeMap.Internal.Impl α β),
      r.size - 1 ≤ r'.size → r'.size ≤ r.size → Std.DTreeMap.Internal.Impl.BalanceLErasePrecond l.size r'.size