How Autoload function on base controller ?

I try to migrate from CI3 to CI4 and my problem is; in CI3 I can call helper function inside MY_Controller but in CI4 it doesn't work.

in MY_Controller.php

PHP Code:

<?php

defined('BASEPATH') or exit('No direct script access allowed');

class MY_Controller extends CI_Controller
{
    public function __construct()
    {
        parent::__construct();
        init_sidebar_menu();
        $data['sidebar'] = $this->sideMenu->getSideMenu();
        $this->load->vars($data);
    }
} 


in my sideMenu Libraries

PHP Code:

<?php

defined('BASEPATH') or exit('No direct script access allowed');

class sideMenu
{
    private $ci;

    private $items = [];

    private $child = [];

    public function __construct()
    {
        $this->ci = &get_instance();
    }

    public function getSideMenu()
    {
        return $this->get('sidebar');
    }

    public function addSidebarMenuItem($slug, $item)
    {
        $this->add($slug, $item, 'sidebar');
        return $this;
    }

    public function add($slug, $item, $group)
    {
        $item = ['slug' => $slug] + $item;

        $this->items[$group][$slug] = $item;
    }

    public function get($group)
    {
        $items = isset($this->items[$group]) ? $this->items[$group] : [];

        foreach ($items as $parent => $item) {
            $items[$parent]['children'] = $this->getChild($parent, $group);
        }

        $items = hooks()->apply_filters("{$group}_menu_items", $items);

        return $items;
    }

    public function getChild($parent_slug, $group)
    {
        $children = isset($this->child[$group][$parent_slug]) ? $this->child[$group][$parent_slug] : [];

        $children = hooks()->apply_filters("{$group}_menu_child_items", $children, $parent_slug);

        return $children;
    }
} 


in my menu helper

PHP Code:

<?php

defined('BASEPATH') or exit('No direct script access allowed');

function init_sidebar_menu()
{
    $CI = &get_instance();

    $CI->sideMenu->addSidebarMenuItem('dashboard', [
        'name'     => 'Dashboard',
        'href'     => base_url(),
        'position' => 1,
        'icon'     => 'fa fa-desktop',
    ]);
} 


How can I call my helper function inside BaseController ?
Because if I use the code above and try to making adjustments to CI4 construction then calling $sidebar var from view, is just show nothing.
Thank you before.