def __init__(self, reset_at="stream", emit_at="stream", mode="eval"):
        """
        Creates an instance of the CumulativeForgetting metric.
        """

        self.classes_splits = {}
        self.classes_seen_so_far = set()

        self.initial = {}
        self.last = {}

        self.train_task_id = None

        super().__init__(
            CumulativeAccuracy(), reset_at=reset_at, emit_at=emit_at, mode=mode
        )

        Creates an instance of the CumulativeForgetting metric.
        
avalanche/evaluation/metrics/cumulative_accuracies.py