Function S2Polygon.initializeToCellUnionBorder

Initialize this polygon to the outline of the given cell union. In principle this polygon should exactly contain the cell union and this polygon's inverse should not intersect the cell union, but rounding issues may cause this not to be the case.

void initializeToCellUnionBorder (
  in const(s2.s2cell_union.S2CellUnion) cells
);