OCA\Richdocuments\Filter::add PHP Method

    public static function add($mimetype, $class)
    {
        self::$filters[$mimetype] = $class;
    }

 public function __construct($mimeSpec)
 {
     $this->readSpec = $mimeSpec['read'];
     $this->writeSpec = $mimeSpec['write'];
     \OCA\Richdocuments\Filter::add($mimeSpec['write']['target'], $this);
 }