code: private String getNTLMHeader(final HttpProxyResponse response) {
          List<String> values = response.getHeaders().get("Proxy-Authenticate");
  
          for (String s : values) {
              if (s.startsWith("NTLM")) {
                  return s;
              }
          }
  
          return null;
      }
docs: Returns the value of the NTLM Proxy-Authenticate header.
  
  @param response the proxy response