Load model codeigniter in Libraries

Question

I’m trying to load the model in Ibraries, but an error is appearing.

Follow the code below:

    <?php

    defined('BASEPATH') OR exit('No direct script access allowed');
    
    class Menu
    {
        private $CI;
        
        public function __construct()
        {
            $this->CI =& get_instance();
            $this->CI->load->model('menu_model');
        }
    
        public function get_all_menu_modulos()
        {
    
            // $this->load->model('Menu_model');
            // $id_group = $this->ion_auth->get_users_groups()->row()->id;
            $id_group = 1;
    
            return $this->menu_model->get_all_menu_id_group($id_group);
        }
    }
    
    ?>

My model:

    <?php

defined('BASEPATH') OR exit('Ação não permitida');

class Menu_model extends CI_Model{

    public function get_menu() {
        $this->db->select([
            'menu_modulos.*'
        ]);
        
        return $this->db->get('menu_modulos')->result();
    }

    public function get_submenu() {
        $this->db->select([
            'menu_modulos.*',
            'menu_modulo_servicos.*'
        ]);
        
        $this->db->join('menu_modulos','menu_modulo_id=menu_modulo_servico_id_menu_modulo','LEFT');
        return $this->db->get('menu_modulo_servicos')->result();

    }

    public function get_all_menu_id_group(){
        $this->db->select([
            'menu_modulos.*',
            'menu_modulo_servicos.*',
            'permissoes.*'
        ]);
    
        $this->db->join('menu_modulo_servicos','menu_modulo_servicos.menu_modulo_servico_id=permissoes.permissao_menu_servico','INNER');
        $this->db->join('menu_modulos','menu_modulos.menu_modulo_id=menu_modulo_servicos.menu_modulo_servico_id_menu_modulo','INNER');
        // $this->db->where('permissoes.permissao_id_group',$id_group);
        return $this->db->get('permissoes')->result();
    }
    
}

The following error appears:

A PHP Error was encountered
Severity: Notice

Message: Undefined property: Menu::$menu_model

Filename: libraries/Menu.php

Line Number: 22

Does anyone have any idea what it might be?