public function getAccessTokenRules()
    {
        if (!is_string($this->accessTokenAttribute) || empty($this->accessTokenAttribute)) {
            return [];
        }
        if (empty($this->accessTokenRules)) {
            $this->accessTokenRules = [
                [[$this->accessTokenAttribute], 'required'],
                [[$this->accessTokenAttribute], 'string', 'max' => 40],
            ];
        }
        return $this->accessTokenRules;
    }