@JsonIgnore
  @JsonProperty(VECTOR_LAYERS_KEY)
  public List<LayerAttrStats.VectorLayer> vectorLayers() {
    return json == null ? null : json.vectorLayers;
  }
Metadata associated with a tile archive.
<p>
The default (de-)serialization corresponds to the
<a href="https://github.com/mapbox/mbtiles-spec/blob/master/1.3/spec.md#metadata">mbtiles spec</a>. As such each
value is a string.
planetiler-core/src/main/java/com/onthegomap/planetiler/archive/TileArchiveMetadata.java