Model/PageCache/ConfigPlugin.php
public function afterGetType(Config $config, $result)
    {
        if (!($config instanceof \Fastly\Cdn\Model\Config)) {
            if ($result == \Fastly\Cdn\Model\Config::FASTLY) {
                return Config::VARNISH;
            }
        }
        return $result;
    }
public function afterGetType(Config $config, $result)
    {
        if (!($config instanceof \Fastly\Cdn\Model\Config)) {
            if ($result == \Fastly\Cdn\Model\Config::FASTLY) {
                return Config::VARNISH;
            }
        }
        return $result;
    }
Return cache type "Varnish" if Fastly is configured.

@param Config $config
@param string $result

@return int