src/Qutee/Worker.php
protected function _sleep()
    {
        // Time ... enough
        if ($this->_getPassedTime() <= $this->_interval) {
            $remainder = ($this->_interval) - $this->_getPassedTime();
            usleep($remainder * 1000000);
        } // Task took more than the interval, don't sleep
    }
protected function _sleep()
    {
        // Time ... enough
        if ($this->_getPassedTime() <= $this->_interval) {
            $remainder = ($this->_interval) - $this->_getPassedTime();
            usleep($remainder * 1000000);
        } // Task took more than the interval, don't sleep
    }
Sleep

@return null