<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def flush(self):
 """ This only needs to be called manually from unit tests """

        self.logger.debug('Flush joining')
        self.queue.join()
        self.logger.debug('Flush joining ready')