docs: def _prune_all_if_small(self, small_size, a_or_u):
          "Return True and delete children if small enough."
          if self._nodes is None:
              return True
  
          total_size = (self.app_size() if a_or_u else self.use_size())
          if total_size < small_size:
              if a_or_u:
                  self._set_size(total_size, self.use_size())
              else:
                  self._set_size(self.app_size(), total_size)
              return True
  
          return False