The function, in the automatic validation of Thinkphp3.2.3 does not execute the method?

this is the code I wrote. In automatic verification, I found that the level field did not implement the checkLevel method. Then I looked at the Tp source code and found that the function section is empty. Is it the tp source code or the problem with my writing?
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tp
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Php
Mar.03,2021

Model class

<?php

namespace Home\Controller;

use Think\Controller;

class AdminController extends Controller
{

    public function addData()
    {
        $data = [
            'username' => 'xiaoming',
            'password' => 'root',
            'email'    => 'test@1.com',
            'level'    => '',
        ];

        $admin = D('Admin');

        if ($admin->create($data))
        {
            echo '';
        }
        else
        {
            dump($admin->getError());
        }
    }
}

result returned

string (21) "Grade data error!"

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