a single sample, shape (num_points, 2).
        flatten_target: A flattened target tensor referring to a single sample, shape (num_points, 2).
        cat_id_to_continuous_id: Mapping from original category IDs to continuous IDs
        void_color: an additional, unused color.
        stuffs_modified_metric: Set of stuff category IDs for which the PQ metric is computed using the "modified"
            formula. If not specified, the original formula is used for all categories.

    Returns:
        - IOU Sum
        - True positives
        - False positives
        - False negatives.

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