def _set_options(self):
        "sets the graph ploting options"
        # this is aweful
        # FIXME: Axis options should be passed completly by a GraphOption
        if 'xaxis' in self._options.keys():
            self._options['xaxis'].update(
                        {'mode' : self._get_axis_mode(XAxis._var_name)})
        if 'yaxis' in self._options.keys():
            self._options['yaxis'].update(
                        {'mode' : self._get_axis_mode(YAxis._var_name)})
sets the graph ploting options