* 2014.08.02 update *
If you need a python code right away, then please keep in touch with https://github.com/carpedm20/LINE
Finally, I want to talk about session key and auth key.
5. Session key
At first, I tried to follow UpdateAuthToken() function because this function adds the "X-Line-Access" header to the HTTP protocol.
As I followed this function, I finally arrived to create() function which updates the old session key.
It wasn't hard to understand how this function updates authKey, but I couldn't figure out when LINE change an auth key.
It seems like LINE's session key is changed when a user change his/her mobile phone or re-install the application.
In other words, the session key won't be changed if you don't erase or change your mobile phone.
This can cause security problems if someone change the code of LINE application and distribute it to the internet...but I don't think it will happen :)
Bellow is the list of functions that I followed to find out how LINE update their authorization key.
Anyway, I wrote an C# code that make updated session key...