=& get_instance in MY_Exceptions

[eluser]freshface[/eluser]
How can i use $this->ci =& get_instance();

Code:

<?php
class MY_Exceptions extends CI_Exceptions
{
    var $ci;
    
    public function __construct()
    {
        parent::CI_Exceptions();
        $this->ci =& get_instance();
    }

    function show_404($page = '')
    {
    
        //lredirect('_404');
        //redirect('error_404','refresh');  // you can change this with what you want
        $content = $this->ci->db->get_where('pages',array('type' => '404', 'language_id' => LANG_ID))->row();
        if(count($content))
        {
            lredirect($content->slug);
        }
        else // failsave
        {
            $heading = "404 Page Not Found";
            $message = "The page you requested was not found.";

            log_message('error', '404 Page Not Found --> '.$page);
            echo $this->show_error($heading, $message, 'error_404');
        }

        exit;
    }
}

Without getting this error: Fatal error: Call to undefined function get_instance() in /Applications/MAMP/htdocs/albatross/app_frontend/libraries/MY_Exceptions.php on line 9