try
Recover the pyramid LevelSet for an image / vector-tile cache, or null when the backend can't reconstruct one (e.g. JS / iOS where the schema doesn't persist the level-set descriptors). Used by the cross-platform reopen dispatcher to rebuild a layer's level-set after restart; callers fall back to a sensible default (slippy-map 0..21) when this returns null.
GeoPackage-backed managers override this and read gpkg_tile_matrix_set / gpkg_tile_matrix. Other backends keep the default no-op until they grow their own per-content schema.