Helper/Config.php
protected function getAdditionalConfigString($storeId = null)
    {
        return $this->getScopeConfig()->getValue(
            self::XML_PATH_ADDITIONAL_CONFIG,
            ScopeInterface::SCOPE_STORE,
            $storeId
        ) ?: '{}';
    }
protected function getAdditionalConfigString($storeId = null)
    {
        return $this->getScopeConfig()->getValue(
            self::XML_PATH_ADDITIONAL_CONFIG,
            ScopeInterface::SCOPE_STORE,
            $storeId
        ) ?: '{}';
    }
protected function getAdditionalConfigString ( $ storeId = null ) { return $ this -> getScopeConfig ( ) -> getValue ( self :: XML_PATH_ADDITIONAL_CONFIG , ScopeInterface :: SCOPE_STORE , $ storeId ) ? : '{}' ; }
Get Additional Config string

@param int|string $storeId

@return  string
Get Additional Config string