string(257) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%9B%B4%E7%BB%95%E4%B8%AD%E5%BF%83%E5%8F%A5%E5%86%99%E4%B8%80%E6%AE%B5%E8%AF%9D%E7%9A%84%E4%BD%9C%E7%94%A8 => Received HTTP code 403 from proxy after CONNECT"
围绕中心句写一段话的作用
