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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 best_actions(self):
 """A tuple containing the actions whose action sets have the best prediction."""

        if self._best_actions is None:
            best_prediction = self.best_prediction
            self._best_actions = tuple(
                action
                for action, action_set in self._action_sets.items()
                if action_set.prediction == best_prediction
            )
        return self._best_actions