def __init__(self, gpus, scale_gradient=True):
        """
        Args:
            gpus ([int]): list of GPU ids.
            scale_gradient (bool): if True, will scale each gradient by ``1.0/nr_gpu``.
        """
        self.devices = gpus
        self._builder = AsyncMultiGPUBuilder(gpus, scale_gradient)
        super(AsyncMultiGPUTrainer, self).__init__()

        Args:
            gpus ([int]): list of GPU ids.
            scale_gradient (bool): if True, will scale each gradient by ``1.0/nr_gpu``.
        
tensorpack/train/trainers.py