Interlaced: PlainDescriptor<
    {
        new_region_ids: FixedSizeArray<
            2,
            { begin: number; core: number; mask: FixedSizeBinary<10> },
        >;
        old_region_id: { begin: number; core: number; mask: FixedSizeBinary<10> };
    },
>

A Region has been converted into two overlapping Regions each of lesser regularity.

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