@abc.abstractmethod
    def schedule(self, plugin, context, router_id,
                 candidates=None, hints=None):
        pass
Whether the track is a placeholder for a non-track object in the
dataset/ETHPy150Open openstack/neutron/neutron/scheduler/l3_agent_scheduler.py/L3Scheduler.schedule--crossover with--dataset/ETHPy150Open mopidy/pyspotify/spotify/track.py/Track.is_placeholder