docs: def submit(self, *items):
  		"""Return job ids assigned to the submitted items."""
  		with self.lock:
  			if self.closed:
  				raise BrokenPipe('Job submission has been closed.')
  			id = self.jobcount
  			self._status += ['SUBMITTED'] * len(items)
  			self.jobcount += len(items)
  			for item in items:
  				self.waitqueue.put((id, item))
  				id += 1
  		if len(items) == 1:
  			return id - 1
  		else:
  			return range(id - len(items), id)