def __init__(self):
        """
        Creates an instance of the WeightCheckpoint Metric.

        By default this metric in its initial state will return None.
        The metric can be updated by using the `update` method
        while the current experience's weight checkpoint tensor can be
        retrieved using the `result` method.
        """
        super().__init__()
        self.weights: Optional[bytes] = None

        Creates an instance of the WeightCheckpoint Metric.

        By default this metric in its initial state will return None.
        The metric can be updated by using the `update` method
        while the current experience's weight checkpoint tensor can be
        retrieved using the `result` method.
        
avalanche/evaluation/metrics/checkpoint.py