def _advanceOffset(self, data):
        self.offset += len(data)
        return data
Opts a user into one of many choices for an experiment. They have a
dataset/ETHPy150Open girder/girder/girder/utility/ziputil.py/ZipGenerator._advanceOffset--crossover with--dataset/ETHPy150Open dailymuse/oz/oz/bandit/middleware.py/BanditTestingMiddleware.choose_experiment