def run(self, incremental=None, run_id=None):
        """Queue the execution of a particular crawler."""
        state = {
            'crawler': self.name,
            'run_id': run_id,
            'incremental': settings.INCREMENTAL
        }
        if incremental is not None:
            state['incremental'] = incremental

        # Cancel previous runs:
        self.cancel()
        # Flush out previous events:
        Event.delete(self)
        Queue.queue(self.init_stage, state, {})
Queue the execution of a particular crawler.