public function addClassFilter($classes)
    {
        if (is_array($classes) && count($classes) !== 0) {
            $filters = array();
            foreach ($classes as $class) {
                class_exists($class);
                $filters[] = 'cc INSTANCE OF \''.  $class .'\'';
            }

            $filter = implode(' OR ', $filters);

            $this->andWhere($filter);
        }
    }