codeigniter

// MINHA MY MODEL -------------

<?php

class MY_Model extends CI_Model
{

    protected $db2;

    public function __construct() {

        parent::__construct();
        $this->connect();
    }


  public function __destruct() {

        $this->db->close();
    }

    public function connect(){

         $second = array(
                         'dsn'   => '',
                         'hostname' => 'localhost',
                         'username' => 'root',
                         'password' => '',
                         'database' => 'nomebanco',
                         'dbdriver' => 'mysqli',
                         'dbprefix' => '',
                         'pconnect' => FALSE,
                         'db_debug' => (ENVIRONMENT !== 'production'),
                         'cache_on' => FALSE,
                         'cachedir' => '',
                         'char_set' => 'utf8',
                         'dbcollat' => 'utf8_general_ci',
                         'swap_pre' => '',
                         'encrypt' => FALSE,
                         'compress' => FALSE,
                         'stricton' => FALSE,
                         'failover' => array(),
                         'save_queries' => TRUE
        );

         $this->db2 = $this->load->database( $second );
    }

}



// MINHA MODEL EXTENDS MY MODEL --------------------

class Schedule_model extends MY_Model{


	public function __construct()
	{
		parent::__construct();
	}





/**
* ------------------------------------------------------------------------------------------
* Function select plan related to user id
* ------------------------------------------------------------------------------------------
*
* @var strings
* @param $idClient
*
*/

	public function listQueryRequests( $idClient )
	{

	   return $this->db2->select( '*' )->from( 'tbl_schedule_temporary' )

	   ->where( 'id_client_system', $idClient )->where('check_flag IN( 0, 1 )' )

	   ->get()->result();


 	}

Aí da esse erro
Message: Call to a member function select() on boolean