models/classes/runner/RunnerParamParserTrait.php
protected function endItemTimer($timestamp = null)
    {
        if($this->getRequestParameter('itemDuration')){
            $serviceContext    = $this->getServiceContext();
            $itemDuration      = $this->getRequestParameter('itemDuration');
            return $this->getRunnerService()->endTimer($serviceContext, $itemDuration, $timestamp);
        }
        return false;
    }
protected function endItemTimer($timestamp = null)
    {
        if($this->getRequestParameter('itemDuration')){
            $serviceContext    = $this->getServiceContext();
            $itemDuration      = $this->getRequestParameter('itemDuration');
            return $this->getRunnerService()->endTimer($serviceContext, $itemDuration, $timestamp);
        }
        return false;
    }
End the item timer to QtiTimeLine

@param null $timestamp The start of action, optional
@return bool