def __init__(self, average=True):
        """
        Args:
            average (bool): whether to average or sum the gradients across processes.
        """
        import byteps.tensorflow as bps
        self.hvd = bps  # BytePS has the same interface as Horovod
        self.hvd.allreduce = bps.push_pull  # https://github.com/bytedance/byteps/issues/8
        assert os.environ.get("DMLC_ROLE", None) == "worker"
        assert "DMLC_WORKER_ID" in os.environ and "DMLC_NUM_WORKER" in os.environ
        bps.init()
        self.is_chief = bps.rank() == 0

        self._local_rank = bps.local_rank()
        self._rank = bps.rank()
        self._average = average

        self._compression = None
        self._has_compression = False
        logger.info("[BytePSTrainer] local rank={}".format(self._local_rank))
        SingleCostTrainer.__init__(self)

        Args:
            average (bool): whether to average or sum the gradients across processes.
        
tensorpack/train/trainers.py