boolean isCollapsed() {
      return coordinates.size() < 2 ||
        (coordinates.size() == 2 && coordinates.getFirst().equals(coordinates.getLast()));
    }
Processes the added geometries and returns the merged linestrings.
<p>
Can be called more than once.
planetiler-core/src/main/java/com/onthegomap/planetiler/util/LoopLineMerger.java