docs: def cleanup(self):
          """Used internally.
  
          Cleans up the sched references in the proactor. If you use this don't use
          it while the :class:`Scheduler` (:func:`run`) is still running.
          """
  
          if hasattr(self, 'proactor'):
              if hasattr(self.proactor, 'scheduler'):
                  del self.proactor.scheduler
              if hasattr(self.proactor, 'close'):
                  self.proactor.close()