code: def private_download_url(self, url, expires=3600):
          
          deadline = int(time.time()) + expires
          if '?' in url:
              url += '&'
          else:
              url += '?'
          url = '{0}e={1}'.format(url, str(deadline))
  
          token = self.token(url)
          return '{0}&token={1}'.format(url, token)
docs: 生成私有资源下载链接
  
          Args:
              url:     私有空间资源的原始URL
              expires: 下载凭证有效期，默认为3600s
  
          Returns:
              私有资源的下载链接