def __init__(self, classes=None, streams=None, ignore_validation=True):
        """
        Instantiates the AMCA plugin metric.

        :param classes: The classes to track. Refer to :class:`MultiStreamAMCA`
            for more details.
        :param streams: The streams to track. Defaults to None, which means that
            all streams will be considered. Beware that, when creating instances
            of this class using the :func:`amca_metrics` helper, the resulting
            metric will only track the "test" stream by default.
        :param ignore_validation: Defaults to True, which means that periodic
            evaluations will be ignored (recommended).
        """
        self._ms_amca = MultiStreamAMCA(classes=classes, streams=streams)
        self._ignore_validation = ignore_validation

        self._is_training = False
        super().__init__(self._ms_amca, reset_at="never", emit_at="stream", mode="eval")

        Instantiates the AMCA plugin metric.

        :param classes: The classes to track. Refer to :class:`MultiStreamAMCA`
            for more details.
        :param streams: The streams to track. Defaults to None, which means that
            all streams will be considered. Beware that, when creating instances
            of this class using the :func:`amca_metrics` helper, the resulting
            metric will only track the "test" stream by default.
        :param ignore_validation: Defaults to True, which means that periodic
            evaluations will be ignored (recommended).
        
avalanche/evaluation/metrics/amca.py