docs: public Set<Class<? extends GrammaticalRelationAnnotation>> arcLabelsToNode(TreeGraphNode destNode) {
      Set<Class<? extends GrammaticalRelationAnnotation>> arcLabels = Generics.newHashSet();
      CyclicCoreLabel cl = label();
      for (Iterator<Class<?>> it = cl.keySet().iterator(); it.hasNext();) {
        Class<? extends CoreAnnotation> key = (Class<? extends CoreAnnotation>) it.next();//javac doesn't compile properly if generics are fully specified (but eclipse does...)
        Object val = cl.get(key);
        if (val != null && val instanceof Set) {
          if (((Set) val).contains(destNode)) {
            if (key != null) {
              arcLabels.add((Class<? extends GrammaticalRelationAnnotation>) key);
            }
          }
        }
      }
      return arcLabels;
    }