/**
  * Returns the URI of the icon of the provided content.
  * 
  * @param  AbstractContent $content The content.
  * 
  * @return string|null              The icon URL if found, null otherwise.
  */
 public function getIcon(AbstractContent $content)
 {
     if (null === ($property = $content->getProperty('iconized-by'))) {
         return null;
     }
     return $this->parseProperty($content, $property);
 }