Function S2RegionCoverer.canonicalizeCovering
Modify "covering" if necessary so that it conforms to the current covering parameters (max_cells, min_level, max_level, and level_mod). There are no restrictions on the input S2CellIds (they may be unsorted, overlapping, etc).
s2 .s2cell_union .S2CellUnion canonicalizeCovering
(
in const(s2 .s2cell_union .S2CellUnion) covering
);