@Override
 public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
   builder.startObject();
   builder.field(FIELD_TYPE, TYPE.shapename);
   builder.startArray(FIELD_GEOMETRIES);
   for (ShapeBuilder shape : shapes) {
     shape.toXContent(builder, params);
   }
   builder.endArray();
   return builder.endObject();
 }