code: def graceful_stop(self, signal_number=None, stack_frame=None):
          
          stop_msg = "Hard" if self.shutdown else "Graceful"
          if signal_number is None:
              self.log.info("%s stop called manually. "
                            "Shutting down.", stop_msg)
          else:
              self.log.info("%s stop called by signal #%s. Shutting down."
                            "Stack Frame: %s",
                            stop_msg, signal_number, stack_frame)
          self.shutdown = True
          self.crawler_list.stop()
          self.daemon_list.stop()
          self.thread_event.set()
          return True
docs: This function will be called when a graceful-stop is initiated.