src/transformers/optimization.py/AdafactorSchedule/get_lr
class AdafactorSchedule:    def get_lr(self):
        opt = self.optimizer
        lrs = [
            opt._get_lr(group, opt.state[group["params"][0]])
            for group in opt.param_groups
            if group["params"][0].grad is not None
        ]
        if len(lrs) == 0:
            lrs = self.base_lrs  # if called before stepping
        return lrs