'Return extra arguments needed on auth process, setting is per
backend and defined by:
<backend name in uppercase>_AUTH_EXTRA_ARGUMENTS.
The defaults can be overriden by GET parameters.'

def auth_extra_arguments(self):

    backend_name = self.AUTH_BACKEND.name.upper().replace('-', '_')
    extra_arguments = setting((backend_name + '_AUTH_EXTRA_ARGUMENTS'), {})
    for (key, value) in six.iteritems(extra_arguments):
        if (key in self.data):
            extra_arguments[key] = self.data[key]
        elif value:
            extra_arguments[key] = value
    return extra_arguments
