def __call__(self, num_update):
    updated_lr = (self.base_lr * (self.factor ** (num_update / self.step)))
    return sym.clip(updated_lr, a_min=self.stop_factor_lr, a_max=self.base_lr)
def __call__(self, num_update):
    updated_lr = (self.base_lr * (self.factor ** (num_update / self.step)))
    return sym.clip(updated_lr, a_min=self.stop_factor_lr, a_max=self.base_lr)