public Map<GraphNode,GraphNode> buildHiddenNodeMap(){
  Map<GraphNode,GraphNode> result=Maps.newHashMap();
  for (  CollapseData masterData : collapsedData.values()) {
    Collection<GraphNode> masterNodes=Lists.newArrayList();
    masterData.addMemberNodes(masterNodes);
    for (    GraphNode childNode : masterNodes) {
      result.put(childNode,masterData.getMasterNode());
    }
  }
  return result;
}

public Map < GraphNode , GraphNode > buildHiddenNodeMap ( ) { Map < GraphNode , GraphNode > result = Maps . newHashMap ( ) ; for ( CollapseData masterData : collapsedData . values ( ) ) { Collection < GraphNode > masterNodes = Lists . newArrayList ( ) ; masterData . addMemberNodes ( masterNodes ) ; for ( GraphNode childNode : masterNodes ) { result . put ( childNode , masterData . getMasterNode ( ) ) ; } } return result ; }
build a map of hidden nodes to their top - level master nodes . this is often used to filter exposed nodes and edges .
