public static function get_instance()
 {
     if (is_null(self::$_instance)) {
         self::$_instance = new self();
     }
     return self::$_instance;
 }
 public function __construct()
 {
     parent::__construct();
     add_action('wp_loaded', array($this, 'register_plugin_for_activation'), 99);
     add_action('admin_init', array($this, 'register_plugin_for_updates'));
     add_filter('ywcps_animate_styles', array($this, 'add_animation_premium'), 10, 1);
     add_action('admin_init', array($this, 'add_free_slider_in_table'));
     add_action('admin_enqueue_scripts', array($this, 'include_admin_premium_style_script'));
 }