def clear(self):
    """Clears the state to prepare for a fresh evaluation."""
    self._evaluation = ObjectDetectionEvaluation(
        num_groundtruth_classes=self._num_classes,
        matching_iou_threshold=self._matching_iou_threshold,
        use_weighted_mean_ap=self._use_weighted_mean_ap,
        label_id_offset=self._label_id_offset)
    self._image_ids.clear()