public static function getSubclasses()
    {
        $subclasses = array();
        foreach (get_declared_classes() as $class) {
            if (method_exists($class, 'isLoadable') && $class::isLoadable() === false) {
                continue;
            }
            if (is_subclass_of($class, 'Taco\Post')) {
                $subclasses[] = $class;
            }
        }
        return $subclasses;
    }