clone.setNotRestartable();
clone.setRestartable(false);
    public NodeIterator cloneIterator() {	try {	    final FilteredStepIterator clone =		(FilteredStepIterator)super.clone();	    clone._source = _source.cloneIterator();	    clone._iterator = _iterator.cloneIterator();	    clone._filter = _filter;	    clone.setNotRestartable();	    return clone.reset();	}	catch (CloneNotSupportedException e) {	    BasisLibrary.runTimeError(BasisLibrary.ITERATOR_CLONE_ERR,				      e.toString());	    return null;	}    }