@Override
 public boolean initialisationComplete(
     TIndexedCollection<DAGNode> nodes, TIndexedCollection<DAGEdge> edges, boolean forceRebuild) {
   if (taggedNodes_ == null) {
     taggedNodes_ = MultiMap.createSortedSetMultiMap();
     TIntObjectIterator<DAGNode> iter = nodes.iterator();
     for (int i = nodes.size(); i-- > 0; ) {
       iter.advance();
       DAGNode n = iter.value();
       String[] props = n.getProperties();
       for (String prop : props) {
         if (prop.startsWith(TAG_PREFIX)) {
           taggedNodes_.put(prop, n);
         }
       }
     }
   }
   return super.initialisationComplete(nodes, edges, forceRebuild);
 }