/**
  * Detach all links from the node and from the other connecting node, storing the connection
  * information in local data structures.
  */
 private void detachLinks() {
   links = new ArrayList<OPPLink>();
   linkSources = new HashMap<OPPLink, OPPNode>();
   linkTargets = new HashMap<OPPLink, OPPNode>();
   links.addAll(node.getIncomingLinks());
   links.addAll(node.getOutgoingLinks());
   for (OPPLink link : links) {
     linkSources.put(link, link.getSource());
     linkTargets.put(link, link.getTarget());
     link.setSource(null);
     link.setTarget(null);
     link.setOpd(null);
   }
 }