public function queue($item_id = null, $action = null)
    {

        if( is_null($item_id) ) {
            throw new NoItemException("No item id was sent");
        } else if ( ! is_numeric($item_id) ){
            throw new InvalidItemTypeException("The item id: $item_id is not valid it should be a number");
        }

        $this->actions[] =
            array(
                'action'        => $action,
                'item_id'       => $item_id,
                'time'          => time()
            );

        return true;

    }