Model/Notification.php
public function checkUpdate($currentVersion = null)
    {
        $lastVersion = $this->getLastVersion();

        if (!$lastVersion || version_compare($lastVersion, $currentVersion, '<=')) {
            return;
        }

        $versionPath = Config::XML_FASTLY_LAST_CHECKED_ISSUED_VERSION;
        $oldValue = $this->scopeConfig->getValue($versionPath);

        if (version_compare($oldValue, $lastVersion, '<')) {
            $this->configWriter->save($versionPath, $lastVersion);

            // save last version in db, and notify only if newly fetched last version is greater than stored version
            $inboxFactory = $this->_inboxFactory;
            $inbox = $inboxFactory->create();
            $inbox->addNotice(
                'Fastly CDN',
                "Version $lastVersion is available. You are currently running $currentVersion."
                    . ' Please consider upgrading at your earliest convenience.'
            );
            $this->cacheManager->clean([\Magento\Framework\App\Cache\Type\Config::TYPE_IDENTIFIER]);
        }
    }
public function checkUpdate($currentVersion = null)
    {
        $lastVersion = $this->getLastVersion();

        if (!$lastVersion || version_compare($lastVersion, $currentVersion, '<=')) {
            return;
        }

        $versionPath = Config::XML_FASTLY_LAST_CHECKED_ISSUED_VERSION;
        $oldValue = $this->scopeConfig->getValue($versionPath);

        if (version_compare($oldValue, $lastVersion, '<')) {
            $this->configWriter->save($versionPath, $lastVersion);

            // save last version in db, and notify only if newly fetched last version is greater than stored version
            $inboxFactory = $this->_inboxFactory;
            $inbox = $inboxFactory->create();
            $inbox->addNotice(
                'Fastly CDN',
                "Version $lastVersion is available. You are currently running $currentVersion."
                    . ' Please consider upgrading at your earliest convenience.'
            );
            $this->cacheManager->clean([\Magento\Framework\App\Cache\Type\Config::TYPE_IDENTIFIER]);
        }
    }
Check feed for modification

@param null $currentVersion