code: def grant_access_token(self):
          
          self._check_appid_appsecret()
  
          if callable(self.__access_token_refreshfunc):
              self.__access_token, self.__access_token_expires_at = self.__access_token_refreshfunc()
              return
  
          response_json = self.__request.get(
              url="https://api.weixin.qq.com/cgi-bin/token",
              params={
                  "grant_type": "client_credential",
                  "appid": self.__appid,
                  "secret": self.__appsecret,
              },
              access_token=self.__access_token
          )
          self.__access_token = response_json['access_token']
          self.__access_token_expires_at = int(time.time()) + response_json['expires_in']
  
          if callable(self.__access_token_setfunc):
              self.__access_token_setfunc(self.__access_token, self.__access_token_expires_at)
  
          return response_json
docs: 获取 access token 并更新当前配置
          :return: 返回的 JSON 数据包 (传入 access_token_refreshfunc 参数后返回 None)