def Authenticate(self, app_id, challenge_data,
                   print_callback=sys.stderr.write):
    """See base class."""
    for authenticator in self.authenticators:
      if authenticator.IsAvailable():
        result = authenticator.Authenticate(app_id,
                                            challenge_data,
                                            print_callback)
        return result

    raise ValueError('No valid authenticators found')
def Authenticate ( self , app_id , challenge_data , print_callback = sys . stderr . write ) : for authenticator in self . authenticators : if authenticator . IsAvailable ( ) : result = authenticator . Authenticate ( app_id , challenge_data , print_callback ) return result raise ValueError ( 'No valid authenticators found' )
See base class.