code: def summary_pairwise_indices(self):
          
          summary_pairwise_indices = np.empty(
              self.values[0].t_stats.shape[1], dtype=object
          )
          summary_pairwise_indices[:] = [
              sig.summary_pairwise_indices for sig in self.values
          ]
          return summary_pairwise_indices
docs: ndarray containing tuples of pairwise indices for the column summary.