code: 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;
    }
docs: Finds all arcs between this node and <code>destNode</code>,
  and returns the <code>Set</code> of <code>Object</code>s which
  label those arcs.  If no such arcs exist, returns an empty
  <code>Set</code>.
  
  @param destNode the destination node
  @return the <code>Set</code> of <code>Object</code>s which
  label arcs between this node and <code>destNode</code>