/**
  * Sets or overrides the default filebase accessible by
  * sfFilebasePlugin::getInstance() sine id argument
  * @param sfFilebasePlugin $filebase
  */
 public static function setDefault(sfFilebasePlugin $filebase)
 {
     if (!array_key_exists($filebase->getId(), self::$instances)) {
         throw new sfFilebasePluginException(sprintf('The filebase identified by %s was not properly registered.', $filebase->getId()));
     }
     self::$instances['default'] = $filebase;
 }