@Override
 public void remove() {
   if (stmt == null) throw new NoSuchElementException();
   ((ContainerI) seq).remove(index - numDeleted, stmt.getObject());
   stmt = null;
   numDeleted++;
 }
 @Override
 public RDFNode next() {
   stmt = base.next();
   index += 1;
   return stmt.getObject();
 }