def read_val(self, key:str) -> Union[List[float],Tuple[List[float],List[float]]]:
        "Read a hyperparameter `key` in the optimizer dictionary."
        val = [pg[key] for pg in self.opt.param_groups[::2]]
        if is_tuple(val[0]): val = [o[0] for o in val], [o[1] for o in val]
        return val
Read a hyperparameter `key` in the optimizer dictionary.