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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 old_status(self, old_status):
 """ Sets the old_status of this BuildSetStatusChangedEvent. :param old_status: The old_status of this BuildSetStatusChangedEvent. :type: str """

        allowed_values = ["NEW", "DONE", "REJECTED"]
        if old_status not in allowed_values:
            raise ValueError(
                "Invalid value for `old_status` ({0}), must be one of {1}"
                .format(old_status, allowed_values)
            )

        self._old_status = old_status