刚学习，用3.2的开发手册试RelationModel 模型，出现以上问题，望高手指点。
IndexController.class.php 代码如下：<?php
namespace Home\Controller;
use Think\Controller;
class IndexController extends Controller {
    public function index(){
       
       $attrs =D("attribute");
       $attrs->relation(Ture)->find(1);
       dump($attrs);
       
       
    }
}IndexModel.class.php 代码如下：<?php
    namespace Home\Model;
    use Think\Model\RelationModel;
    class IndexModel extends RelationModel{

        //定义关联
        protected $_link = array(
            'good_type' => array(
                'mapping_type'  => self::BELONGS_TO, 
                'class_name'   => 'goods_type',  //关联的表名
                'foreign_key'  => 'type_id',  //外键
                'as_fields'    => 'type_name',//获取过来的字段
            ),
        );
    }发生错误如下：

:(
Think\Model:relation方法不存在！
错误位置
FILE: C:\wamp64\www\shopp\ThinkPHP\Library\Think\Model.class.php 　LINE: 257
TRACE
#0 C:\wamp64\www\shopp\ThinkPHP\Library\Think\Model.class.php(257): E('Think\\Model:rel...')
#1 C:\wamp64\www\shopp\Application\Home\Controller\IndexController.class.php(8): Think\Model->__call('relation', Array)
#2 C:\wamp64\www\shopp\Application\Home\Controller\IndexController.class.php(8): Think\Model->relation('Ture')
#3 [internal function]: Home\Controller\IndexController->index()
#4 C:\wamp64\www\shopp\ThinkPHP\Library\Think\App.class.php(178): ReflectionMethod->invoke(object(Home\Controller\IndexController))
#5 C:\wamp64\www\shopp\ThinkPHP\Library\Think\App.class.php(113): Think\App::invokeAction(object(Home\Controller\IndexController), 'index')
#6 C:\wamp64\www\shopp\ThinkPHP\Library\Think\App.class.php(213): Think\App::exec()
#7 C:\wamp64\www\shopp\ThinkPHP\Library\Think\Think.class.php(135): Think\App::run()
#8 C:\wamp64\www\shopp\ThinkPHP\ThinkPHP.php(100): Think\Think::start()
#9 C:\wamp64\www\shopp\index.php(24): require('C:\\wamp64\\www\\s...')
#10 {main}
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