Model/Config.php
public function getVclFile($vclTemplatePath) // @codingStandardsIgnoreLine - Unused parameter required due to compatibility with parent class
    {
        $moduleEtcPath = $this->reader->getModuleDir(Dir::MODULE_ETC_DIR, 'Fastly_Cdn');
        $configFilePath = $moduleEtcPath . '/' . $this->_scopeConfig->getValue(self::FASTLY_CONFIGURATION_PATH);
        $directoryRead = $this->readFactory->create($moduleEtcPath);
        $configFilePath = $directoryRead->getRelativePath($configFilePath);
        $data = $directoryRead->readFile($configFilePath);
        return strtr($data, $this->getReplacements());
    }
public function getVclFile($vclTemplatePath) // @codingStandardsIgnoreLine - Unused parameter required due to compatibility with parent class
    {
        $moduleEtcPath = $this->reader->getModuleDir(Dir::MODULE_ETC_DIR, 'Fastly_Cdn');
        $configFilePath = $moduleEtcPath . '/' . $this->_scopeConfig->getValue(self::FASTLY_CONFIGURATION_PATH);
        $directoryRead = $this->readFactory->create($moduleEtcPath);
        $configFilePath = $directoryRead->getRelativePath($configFilePath);
        $data = $directoryRead->readFile($configFilePath);
        return strtr($data, $this->getReplacements());
    }
Return generated magento2_fastly_varnish.vcl configuration file

@param string $vclTemplatePath
@return string
@throws \Magento\Framework\Exception\FileSystemException