/**
  * Appends the given entry after the entry with the given id, but before the next separator.
  *
  * @param id the id of the entry to append after
  * @param entry the entry to add
  */
 public void appendToSection(String id, PaletteEntry entry) {
   // find the entry with the given id
   boolean found = false;
   for (int i = 0; i < getChildren().size(); i++) {
     PaletteEntry currEntry = (PaletteEntry) getChildren().get(i);
     if (currEntry.getId().equals(id)) found = true;
     else if (found && currEntry instanceof PaletteSeparator) {
       add(i, entry);
       return;
     }
   }
   if (found) add(entry);
   else throw new IllegalArgumentException("Section not found: " + id); // $NON-NLS-1$
 }