How to access additional login parameters with TG2

[Naseem]

Hello

I want an additional parameter 'location' with login and password of
TG2 default authentication system. I have added the field with
login.html, but I don't know how to access it from my code. The login
action goes to login_handler I don't know where it is. I see a
function post_login in rootcontroller, Is there any way to access the
parameters from there ?

Thanks in advance
Naseem