Override Core module Class

[tarek.fellah]

I would like to override the HomeSlide class for the module homeslider, for that I created a file HomeSlide.php and i placed it under override/modules/homeslider. I tried this HomeSlide.php :

class HomeSlide  extends HomeSlideCore{    public $start_date;    public $end_date;    public  function __construct($id_slide = null, $id_lang = null, $id_shop = null, Context $context = null)    {        self::$definition['fields']['start_date'] =   array('type' => self::TYPE_DATE, 'validate' => 'isDate');        self::$definition['fields']['end_date'] =   array('type' => self::TYPE_DATE, 'validate' => 'isDate');        parent::__construct($id_slide, $id_lang, $id_shop);    [spam-filter]

But I got this error

 Class 'HomeSlideCore' not found

Any help would be appreciated. Thanks.