docs: private String placeLayerBelow() {
      if (belowLayer == null || belowLayer.isEmpty()) {
        List<Layer> styleLayers = style.getLayers();
        Layer layer;
        for (int i = styleLayers.size() - 1; i >= 0; i--) {
          layer = styleLayers.get(i);
          if (!(layer instanceof SymbolLayer)) {
            return layer.getId();
          }
        }
      }
      return belowLayer;
    }