/**
  * If Format is string, Size will be formatted (kb, mb ...) 
  *
  * @throws sfFilebasePluginException
  * @param string $format = null | string
  */
 public function getSize($format = null)
 {
     if (!$this->fileExists()) {
         throw new sfFilebasePluginException(sprintf('File %s does not exist.', $this->getPathname()));
     }
     if (!$this->isReadable()) {
         throw new sfFilebasePluginException(sprintf('File %s is not readable.', $this->getPathname()));
     }
     $size = parent::getSize();
     if ($format) {
         return sfFilebasePlugin::getStringFilesize((double) $size);
     }
     return $size;
 }