src/transformers/optimization.py/AdafactorSchedule/__init__
class AdafactorSchedule:    def __init__(self, optimizer, initial_lr=0.0):
        def lr_lambda(_):
            return initial_lr

        for group in optimizer.param_groups:
            group["initial_lr"] = initial_lr
        super().__init__(optimizer, lr_lambda)
        for group in optimizer.param_groups:
            del group["initial_lr"]