'Prototype method to 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):

    if (type(variable) is list):
        variable = '&'.join(variable)
    return INPUT(_type='hidden', _id=('%s-data' % self.attr['_id']), _class=('filter-widget-data    %s-data' % self._class), _value=variable)
