public function extension(Model $model, $data, array $allowed = array()) {
        return $this->_validate($model, $data, 'ext', array($allowed));
    }
public function extension(Model $model, $data, array $allowed = array()) {
        return $this->_validate($model, $data, 'ext', array($allowed));
    }
public function extension ( Model $ model , $ data , array $ allowed = array ( ) ) { return $ this -> _validate ( $ model , $ data , 'ext' , array ( $ allowed ) ) ; }
Validates the extension.

@param Model $model
@param array $data
@param array $allowed
@return bool
Validates the extension .