String formatTable(Function<Number, String> formatter,
      Function<Cell, Number> extractStat) {
      StringBuilder builder = new StringBuilder();
      List<String> layers = layers().stream()
        .sorted(Comparator.comparingInt(this::minZoomWithData))
        .toList();

      // header:   0 1 2 3 4 ... 15
      builder.append(formatRow("", z -> "z" + z, "all")).append('\n');

      // each row: layer
      for (var layer : layers) {
        builder.append(formatRow(
          layer,
          formatter,
          z -> extractStat.apply(get(z, layer)),
          extractStat.apply(get(layer))
        )).append('\n');
      }
      return builder.toString().stripTrailing();
    }
Returns the minimum zoom a specific layer appears at in the tileset.
planetiler-core/src/main/java/com/onthegomap/planetiler/util/TilesetSummaryStatistics.java