code: def query_obj(self):
          
          d = super().query_obj()
          d['row_limit'] = self.form_data.get(
              'row_limit', int(config.get('VIZ_ROW_LIMIT')))
          numeric_columns = self.form_data.get('all_columns_x')
          if numeric_columns is None:
              raise Exception(_('Must have at least one numeric column specified'))
          self.columns = numeric_columns
          d['columns'] = numeric_columns + self.groupby
          # override groupby entry to avoid aggregation
          d['groupby'] = []
          return d
docs: Returns the query object for this visualization