This Gist is created in 2014, and it's highliy outdated now, according to one of mitmproxy
's manjor contributor (check his comment below). Thanks for letting us know, @mhils!
Modern applications usually make use of back-end API servers to provide their services. With a non-transparent HTTPs proxy, which intercepts the communication between clients and servers (aka the man-in-the-middle scheme), you can easily manipulate both API requests and responses.