code: def _exclude_on_fail(self, df):
          
          idx = df if isinstance(df, pd.MultiIndex) else _meta_idx(df)
          self.meta.loc[idx, 'exclude'] = True
          logger().info('{} non-valid scenario{} will be excluded'
                        .format(len(idx), '' if len(idx) == 1 else 's'))
docs: Assign a selection of scenarios as `exclude: True` in meta