from torch.optim.lr_scheduler import StepLR


class StepMinLR(StepLR):
    def __init__(self, optimizer, step_size, gamma=0.1, min_lr=0.0, last_epoch=-1):
        self.min_lr = min_lr
        super().__init__(optimizer, step_size, gamma, last_epoch)

    def get_lr(self):
        # use StepLR's formula, then clamp
        raw_lrs = super().get_lr()
        return [max(lr, self.min_lr) for lr in raw_lrs]