无法找到指定的类：codeigniter中的Session.php

Question

   class Test extends CI_Controller 
   {
     public function __construct()
     {
        parent::__construct();
     }

     public function index()
     {
        $data = array();
        $this->load->library('../controllers/front/booking.php');
        $Booking = new Booking;
        $data['menu'] = $Booking->process_handled_response($sata);
    }
 }

    Booking.php 
    class Booking extends CI_Controller 
    {
       public function __construct() 
       { 
         //calls till here
         parent::__construct();
         // aftr this it doesnt
         $this->load->library(array('session'); 
       }
    }

    public function process_handled_response($data)
    {
        echo "111"; exit;
    }
}

错误：无法找到指定的类：Session.php 测试控制器调用预约控制器功能但它显示上述错误。它加载库并可以调用booking.php直到//调用直到这里 在parent :: __ construct（）之后;它显示错误。