def forgetting_metrics(*, experience=False, stream=False) -> List[PluginMetric]:
    """
    Helper method that can be used to obtain the desired set of
    plugin metrics.

    :param experience: If True, will return a metric able to log
        the forgetting on each evaluation experience.
    :param stream: If True, will return a metric able to log
        the forgetting averaged over the evaluation stream experiences,
        which have been observed during training.

    :return: A list of plugin metrics.
    """

    metrics: List[PluginMetric] = []

    if experience:
        metrics.append(ExperienceForgetting())

    if stream:
        metrics.append(StreamForgetting())

    return metrics

    Helper method that can be used to obtain the desired set of
    plugin metrics.

    :param experience: If True, will return a metric able to log
        the forgetting on each evaluation experience.
    :param stream: If True, will return a metric able to log
        the forgetting averaged over the evaluation stream experiences,
        which have been observed during training.

    :return: A list of plugin metrics.
    
avalanche/evaluation/metrics/forgetting_bwt.py