docs: def refresh_access_token(self, refresh_token):
          """刷新 access token
  
          :param refresh_token: OAuth2 refresh token
          :return: JSON 数据包
          """
          res = self._get(
              'sns/oauth2/refresh_token',
              params={
                  'appid': self.app_id,
                  'grant_type': 'refresh_token',
                  'refresh_token': refresh_token
              }
          )
          self.access_token = res['access_token']
          self.open_id = res['openid']
          self.refresh_token = res['refresh_token']
          self.expires_in = res['expires_in']
          return res