我正在尝试为表建立多对多关系的管理控制器 我发现的解决方案是在对象模型上使用关联，但出现错误 注意：未定义的属性：Doctors :: $ associations 模型是

require_once _PS_ROOT_DIR_.'/modules/tender/override/Hospitals.php';
class Doctors extends ObjectModel{
    //put your code here
    public $id;
    public $name;
    public $odoo_id;
    public $create_time;
    public $update_time;
    public $create_user_id;
    public $update_user_id;

    public static $definition=[
      'table'=>'tender_doctor','primary'=>'id','fields'=>[
            'name'=>['type'=>self::TYPE_STRING,'validation'=>'isAnything','required'=>true],'odoo_id'=>['type'=>self::TYPE_STRING,'create_user_id'=>['type'=>self::TYPE_INT,'required'=>false],'update_user_id'=>['type'=>self::TYPE_INT,'create_time'=>['type'=>self::TYPE_DATE,'update_time'=>['type'=>self::TYPE_DATE,'associations'=>array(
            'doctor_hos' =>array('type' => self::HAS_MANY,'field' => 'id','object' => 'Hospitals','association' => 'tender_doctor_hospital'),),],];
    }