docs: def _update_mean_in_window(self):
          """
          Compute mean in window the slow way. useful for first step.
  
          Considers all values in window
  
          See Also
          --------
          _add_observation_to_means : fast update of mean for single observation addition
          _remove_observation_from_means : fast update of mean for single observation removal
  
          """
          self._mean_x_in_window = numpy.mean(self._x_in_window)
          self._mean_y_in_window = numpy.mean(self._y_in_window)