public function sync($modifiedTime = null, $moduleName = null, $syncType = null)
    {
        $modifiedTime = (empty($modifiedTime))
            ? strtotime('today midnight')
            : intval($modifiedTime);

        $requestData = [
            'modifiedTime' => $modifiedTime
        ];

        if (!empty($moduleName)) {
            $requestData[ 'elementType' ] = $moduleName;
        }

        if ($syncType) {
            $requestData[ 'syncType' ] = $syncType;
        }

        return $this->wsClient->invokeOperation('sync', $requestData, 'GET');
    }