def start_auth(self, context, internal_request, get_state=stateID):
        """
        :param get_state: Generates a state to be used in authentication call

        :type get_state: Callable[[str, bytes], str]
        :type context: satosa.context.Context
        :type internal_request: satosa.internal.InternalData
        :rtype satosa.response.Redirect
        """
        oauth_state = get_state(self.config["base_url"], rndstr().encode())
        context.state[self.name] = dict(state=oauth_state)

        request_args = dict(
            client_id=self.config['client_config']['client_id'],
            redirect_uri=self.redirect_url,
            state=oauth_state,
            allow_signup=self.config.get('allow_signup', False))
        scope = ' '.join(self.config['scope'])
        if scope:
            request_args['scope'] = scope

        cis = self.consumer.construct_AuthorizationRequest(
            request_args=request_args)
        return Redirect(cis.request(self.consumer.authorization_endpoint))
:param get_state: Generates a state to be used in authentication call

        :type get_state: Callable[[str, bytes], str]
        :type context: satosa.context.Context
        :type internal_request: satosa.internal.InternalData
        :rtype satosa.response.Redirect