code: def treeplot(self, qlist, credible_interval):
          
          for y, _, label, values, color in self.iterator():
              ntiles = np.percentile(values.flatten(), qlist)
              ntiles[0], ntiles[-1] = hpd(values.flatten(), credible_interval)
              yield y, label, ntiles, color
docs: Get data for each treeplot for the variable.