'Construct the hidden element that holds the
URL query term corresponding to an input element in the widget.
@param variable: the URL query variable'

def data_element(self, variable):

    output = []
    oappend = output.append
    i = 0
    for level in self.levels:
        widget = INPUT(_type='hidden', _id=('%s-%s-data' % (self.attr['_id'], level)), _class=('filter-widget-data    %s-data' % self._class), _value=variable[i])
        oappend(widget)
        i += 1
    return output
