code: def _polling_iteration(self):
  		
  		if len(self.__task_chain) > 0:
  			if self.__current_task is None:
  				self.__current_task = 0
  
  			task = self.__task_chain[self.__current_task]
  			if task.thread() is None:
  				task.start()
  			elif task.ready_event().is_set() is True:
  				task.stop()
  				if self.__current_task < (len(self.__task_chain) - 1):
  					self.__current_task += 1
  				else:
  					self.ready_event().set()
  			elif task.exception_event().is_set() is True:
  				raise RuntimeError('Child thread failed')
  		else:
  			self.ready_event().set()
docs: :meth:`.WPollingThreadTask._polling_iteration` implementation