public SubstancePredicate makeSubstancePredicate(ArchivalUnit au)
     throws PluginException.LinkageError {
   try {
     return inst.makeSubstancePredicate(au);
   } catch (LinkageError e) {
     throw new PluginException.LinkageError(e);
   }
 }
 public String toString() {
   return "[W: " + inst.toString() + "]";
 }