<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def not_played(self) -> int: """The number of games in the player's promos that they haven't played yet."""

        return len(self._data[MiniSeriesData].progress) - len(self.progress)