void addEdge(Edge edge) {
      for (Edge other : this.edge) {
        if (other.coordinates.equals(edge.coordinates)) {
          return;
        }
      }
      this.edge.add(edge);
    }
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