public function flushQueue() : bool
    {
        $serverPid = $this->getServerPid();
        if (empty($serverPid)) {
            throw new ControlException('Angela not currently running.');
        }
        $response = $this->sendCommand('flush_queue');
        if ($response !== 'ok') {
            throw new ControlException('Error flushing queue. (Incorrect response)');
        }
        return true;
    }