How to decode urllib response data

I'm use urllib craw a https web, the response_header are:

HTTP/1.1 200 OK
Cache-Control: max-age=0
Content-type: application/octet-stream
Transfer-Encoding: chunked
Date: Wed, 07 Nov 2018 07:01:00 GMT
Server: lighttpd

response data are: response data

I know the content type application/octet-stream are not general encoding,but there must be some web js decode those response data,Does anyone know how to find the decode code from the web js or find out which web js file use the response data