code: def make_stacked(self):
          "If unstacked, convert to stacked. If stacked, do nothing."
          if self.stacked:
              return
  
          self._boundaries = bounds = np.r_[0, np.cumsum(self.n_pts)]
          self.stacked_features = stacked = np.vstack(self.features)
          self.features = np.array(
              [stacked[bounds[i-1]:bounds[i]] for i in xrange(1, len(bounds))],
              dtype=object)
          self.stacked = Truf make_stacked(self):
          "If unstacked, convert to stacked. If stacked, do nothing."
          if self.stacked:
              return
  
          self._boundaries = bounds = np.r_[0, np.cumsum(self.n_pts)]
          self.stacked_features = stacked = np.vstack(self.features)
          self.features = np.array(
              [stacked[bounds[i-1]:bounds[i]] for i in xrange(1, len(bounds))],
              dtype=object)
          self.stacked = True
docs: If unstacked, convert to stacked. If stacked, do nothing.