/**
  * Check all nodes to see if their labels are consistent. If any are not, return false
  *
  * @return <code>true</code> if the edge area labels are consistent at this node
  */
 private boolean isNodeEdgeAreaLabelsConsistent() {
   for (Iterator nodeIt = nodeGraph.getNodeIterator(); nodeIt.hasNext(); ) {
     RelateNode node = (RelateNode) nodeIt.next();
     if (!node.getEdges().isAreaLabelsConsistent(geomGraph)) {
       invalidPoint = (Coordinate) node.getCoordinate().clone();
       return false;
     }
   }
   return true;
 }
 /**
  * Checks for two duplicate rings in an area. Duplicate rings are rings that are topologically
  * equal (that is, which have the same sequence of points up to point order). If the area is
  * topologically consistent (determined by calling the <code>isNodeConsistentArea</code>,
  * duplicate rings can be found by checking for EdgeBundles which contain more than one EdgeEnd.
  * (This is because topologically consistent areas cannot have two rings sharing the same line
  * segment, unless the rings are equal). The start point of one of the equal rings will be placed
  * in invalidPoint.
  *
  * @return true if this area Geometry is topologically consistent but has two duplicate rings
  */
 public boolean hasDuplicateRings() {
   for (Iterator nodeIt = nodeGraph.getNodeIterator(); nodeIt.hasNext(); ) {
     RelateNode node = (RelateNode) nodeIt.next();
     for (Iterator i = node.getEdges().iterator(); i.hasNext(); ) {
       EdgeEndBundle eeb = (EdgeEndBundle) i.next();
       if (eeb.getEdgeEnds().size() > 1) {
         invalidPoint = eeb.getEdge().getCoordinate(0);
         return true;
       }
     }
   }
   return false;
 }