def start(self):
        """
        Start the connection pool.

        If you are using the reactor normally, this function does *not*
        need to be called.
        """
        if not self.running:
            self.threadpool.start()
            self.shutdownID = self._reactor.addSystemEventTrigger(
                'during', 'shutdown', self.finalClose)
            self.running = True

        Start the connection pool.

        If you are using the reactor normally, this function does *not*
        need to be called.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/enterprise/adbapi.py