How to use the scenedetect.stats_manager.FrameMetricRegistered function in scenedetect

def test_metrics():
    """ Test StatsManager metric registration/setting/getting with a set of pre-defined
    key-value pairs (metric_dict).
    """
    metric_dict = {'some_metric': 1.2345, 'another_metric': 6.7890}
    metric_keys = list(metric_dict.keys())

    stats = StatsManager()
    frame_key = 100
    assert not stats.is_save_required()

    stats.register_metrics(metric_keys)

    assert not stats.is_save_required()
    with pytest.raises(FrameMetricRegistered):
        stats.register_metrics(metric_keys)

    assert not stats.metrics_exist(frame_key, metric_keys)
    assert stats.get_metrics(frame_key, metric_keys) == [None] * len(metric_keys)

    stats.set_metrics(frame_key, metric_dict)

    assert stats.is_save_required()

    assert stats.metrics_exist(frame_key, metric_keys)
    assert stats.metrics_exist(frame_key, metric_keys[1:])

    assert stats.get_metrics(frame_key, metric_keys) == [
        metric_dict[metric_key] for metric_key in metric_keys]

def add_detector(self, detector):
        """ Add Detector: Adds a detection algorithm to the CliContext's SceneManager. """
        self.check_input_open()
        options_processed_orig = self.options_processed
        self.options_processed = False
        try:
            self.scene_manager.add_detector(detector)
        except scenedetect.stats_manager.FrameMetricRegistered:
            raise click.BadParameter(message='Cannot specify detection algorithm twice.',
                                     param_hint=detector.cli_name)
        self.options_processed = options_processed_orig

""" Register Metrics

        Register a list of metric keys that will be used by the detector.
        Used to ensure that multiple detector keys don't overlap.

        Raises:
            FrameMetricRegistered: A particular metric_key has already been registered/added
                to the StatsManager. Only if the StatsManager is being used for read-only
                access (i.e. all frames in the video have already been processed for the given
                metric_key in the exception) is this behavior desirable.
        """
        for metric_key in metric_keys:
            if metric_key not in self._registered_metrics:
                self._registered_metrics.add(metric_key)
            else:
                raise FrameMetricRegistered(metric_key)

def add_detector(self, detector):
        """ Add Detector: Adds a detection algorithm to the CliContext's SceneManager. """
        self.check_input_open()
        options_processed_orig = self.options_processed
        self.options_processed = False
        try:
            self.scene_manager.add_detector(detector)
        except scenedetect.stats_manager.FrameMetricRegistered:
            raise click.BadParameter(message='Cannot specify detection algorithm twice.',
                                     param_hint=detector.cli_name)
        self.options_processed = options_processed_orig

# type: (SceneDetector) -> None
        """ Adds/registers a SceneDetector (e.g. ContentDetector, ThresholdDetector) to
        run when detect_scenes is called. The SceneManager owns the detector object,
        so a temporary may be passed.

        Arguments:
            detector (SceneDetector): Scene detector to add to the SceneManager.
        """
        detector.stats_manager = self._stats_manager
        if self._stats_manager is not None:
            # Allow multiple detection algorithms of the same type to be added
            # by suppressing any FrameMetricRegistered exceptions due to attempts
            # to re-register the same frame metric keys.
            try:
                self._stats_manager.register_metrics(detector.get_metrics())
            except FrameMetricRegistered:
                pass

        if not issubclass(type(detector), SparseSceneDetector):
            self._detector_list.append(detector)
        else:
            self._sparse_detector_list.append(detector)

def __init__(self, metric_key, message="Attempted to re-register frame metric key."):
        # type: (str, str)
        # Pass message string to base Exception class.
        super(FrameMetricRegistered, self).__init__(message)
        self.metric_key = metric_key