def mapper_pre_filter(self):
        raise NotImplementedError
Processes an incoming BCP 'switch' command.
dataset/ETHPy150Open Yelp/mrjob/mrjob/job.py/MRJob.mapper_pre_filter--crossover with--dataset/ETHPy150Open missionpinball/mpf/mpf/media_controller/core/media_controller.py/MediaController.bcp_switch