class RemovableKeySet extends KeySet {

    @Override
    public boolean remove(Object o) {
        String skey = key(o);
        Object previous = request.getValue(skey);
        if (previous != null) {
            request.removeValue(skey);
            return true;
        }
        return false;
    }

    public  RemovableKeySet(HasRemovableKeys<?> request);

}