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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _advance_window(self):
 """Update values in current window and the current window means and variances."""

        x_to_remove, y_to_remove = self._x_in_window[0], self._y_in_window[0]

        self._window_bound_lower += 1
        self._update_values_in_window()
        x_to_add, y_to_add = self._x_in_window[-1], self._y_in_window[-1]

        self._remove_observation(x_to_remove, y_to_remove)
        self._add_observation(x_to_add, y_to_add)