code: def get_new_message_num(self, lastid=0):
          
          url = 'https://mp.weixin.qq.com/cgi-bin/getnewmsgnum?f=json&t=ajax-getmsgnum&lastmsgid={lastid}&token={token}&lang=zh_CN'.format(
              lastid=lastid,
              token=self.__token,
          )
          payloads = {
              'ajax': 1,
              'f': 'json',
              'random': random.random(),
              'lang': 'zh_CN',
              'token': self.__token,
          }
          headers = {
              'x-requested-with': 'XMLHttpRequest',
              'referer': 'https://mp.weixin.qq.com/cgi-bin/message?t=message/list&count=20&day=7&token={token}&lang=zh_CN'.format(
                  token=self.__token,
              ),
              'cookie': self.__cookies,
          }
          r = requests.get(url, data=payloads, headers=headers)
  
          try:
              return int(json.loads(r.text)['newTotalMsgCount'])
          except (KeyError, ValueError):
              raise NeedLoginError(r.text)
docs: 获取新消息的数目
          :param lastid: 最近获取的消息 ID, 为 0 时获取总消息数目
          :return: 消息数目