Controllers Codeigniter (parents)?

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PHP

CodeIgniter

Hello! I created my own class at folder applications/core and named it MY_Output.php

class MY_Output extends CI_Output {

    function set_status_header($code = 200, $text = '')
    {
        set_status_header($code, $text);
        $this->last_set_status_code = $code;
        return $this;
    }

    function get_status_header()
    {
        return $this->last_set_status_code;
    }

}

At folder controllers i created new controller Error.php:
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Error extends MY_Output 
{
	public function __construct()
	{
		parent::__construct();
	}

	function error_404()
	{
		
			$this->load->view('404');
	}
}       

?>  

How i can get access (call) to functions of class MY_Output from class Error?