def __init__(self, stages):
        if len(stages) < 2:
            raise ValueError(u'pipeline must have at least two stages')
        self.stages = []
        for stage in stages:
            if isinstance(stage, (list, tuple)):
                self.stages.append(stage)
            else:
                # Default to one thread per stage.
                self.stages.append((stage,))
Given an interval, return the values list between two given positions.
dataset/ETHPy150Open beetbox/beets/beets/util/pipeline.py/Pipeline.__init__--crossover with--dataset/ETHPy150Open taoliu/MACS/MACS2/IO/BinKeeper.py/BinKeeperII.pp2pvs