def __init__(self, net):
    super(BackwardNet, self).__init__(auto_prefix=False)
    self.forward_net = net
    self.grad = C.GradOperation(get_all=True)
def __init__(self, net):
    super(BackwardNet, self).__init__(auto_prefix=False)
    self.forward_net = net
    self.grad = C.GradOperation(get_all=True)