code: def process_incoming_tuples(self):
      
      # back-pressure
      if self.output_helper.is_out_queue_available():
        self._read_tuples_and_execute()
        self.output_helper.send_out_tuples()
      else:
        # update outqueue full count
        self.bolt_metrics.update_out_queue_full_count()
docs: Should be called when tuple was buffered into in_stream
  
      This method is equivalent to ``addBoltTasks()`` but
      is designed for event-driven single-thread bolt.