K, how about this:

1. init global variable from __init__(): self.extraAuth = None
2. add a set_extraAuth(self, otp, gauth): 
       #feed global variable here
3. From send_request(): check global variable and add it to params regarding the content.

So people can:
fas = AccountSystem()
fas.set_extraAuth(otp=xxxxxxxxxxxxx)
fas.person_by_name()