docs: def upregulated(self, thresh=0.05, idx=True):
          """
          Upregulated features.
  
          {threshdoc}
          """
          ind = (
              (self.data[self.pval_column] <= thresh)
              & (self.data[self.lfc_column] > 0)
          )
          if idx:
              return ind
          return self[ind]