如何在codeigniter中将我的upload函数转置为Helper？

<?php
function upload_file($config)
{
    $CI =& get_instance();
    $CI->load->library('upload', $config);
    
    if (!$CI->upload->do_upload('file')) {
        $error = $CI->upload->display_errors();
        return $error;
    } else {
        $data = $CI->upload->data();
        return $data;
    }
}

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Your_controller extends CI_Controller {

    public function __construct()
    {
        parent::__construct();
        $this->load->helper('upload');
    }

    public function upload_file()
    {
        $config['upload_path'] = './uploads/';
        $config['allowed_types'] = 'gif|jpg|png';
        $config['max_size'] = 100;
        
        $result = upload_file($config);
        
        if (is_string($result)) {
            echo $result; // 上传失败，打印错误信息
        } else {
            print_r($result); // 上传成功，打印上传文件的信息
        }
    }
}