static <T extends OsmElement> Block of(Iterable<T> items) {
      return () -> {
        @SuppressWarnings("unchecked") Iterable<OsmElement> iterable = (Iterable<OsmElement>) items;
        return iterable;
      };
    }
Create a fake block from existing elements - useful for tests.
planetiler-core/src/main/java/com/onthegomap/planetiler/reader/osm/OsmBlockSource.java