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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 _set_payoff(self, payoff):
 """Setter method for the payoff property."""

        if self._selected_action is None:
            raise ValueError("The action has not been selected yet.")
        if self._closed:
            raise ValueError("The payoff for this match set has already"
                             "been applied.")
        self._payoff = float(payoff)