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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 stats(self):
 """The current status of the positions. Returns ------- stats : PositionStats The current stats position stats. Notes ----- This is cached, repeated access will not recompute the stats until the stats may have changed. """

        if self._dirty_stats:
            calculate_position_tracker_stats(self.positions, self._stats)
            self._dirty_stats = False

        return self._stats