private List<Transformer> initEdgeTransformers() {
   List<Transformer> res = new ArrayList<Transformer>();
   for (Transformer transformer : Lookup.getDefault().lookupAll(Transformer.class)) {
     if (transformer.isEdge()) {
       res.add(transformer);
     }
   }
   return res;
 }
 protected String getId(Transformer transformer, Column column) {
   return getIdPrefix()
       + "_"
       + transformer.getClass().getSimpleName()
       + "_column_"
       + column.getId();
 }
 protected String getId(Transformer transformer, String suffix) {
   return getIdPrefix() + "_" + transformer.getClass().getSimpleName() + "_" + suffix;
 }
 protected TransformerUI getTransformerUI(Transformer transformer) {
   return transformerUIs.get(transformer.getClass());
 }