How to check if the proxy have a high anonymity level or a transparent level in Python? 
I am writing a script to sort the good proxies but I want to filter only the high anonymity ones (elite proxies).
Launch test site in the internet. It will perform only one operation: save received request with all the headers into a database or a file. Each request should have your signature to be sure it's yours original request.
Connect with your Python script via proxy being tested to the site. Send all headers you want to see on that side.
Check data received - are there some headers or some date what can break your anonymity.
How to check proxy's anonymity level?