def check_actors(self, actors):
        """
        Performs checks on the actors that are to be used. Raises an exception if invalid setup.

        :param actors: the actors to check
        :type actors: list
        """
        super(Flow, self).check_actors(actors)
        actor = self.first_active
        if (actor is not None) and not base.is_source(actor):
            raise Exception("First active actor is not a source: " + actor.full_name)
Performs checks on the actors that are to be used. Raises an exception if invalid setup.

        :param actors: the actors to check
        :type actors: list