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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 reason(self, reason):
 """ Sets the reason of this ServicePackageQuotaHistoryItem. Type of quota usage entry. :param reason: The reason of this ServicePackageQuotaHistoryItem. :type: str """

        if reason is None:
            raise ValueError("Invalid value for `reason`, must not be `None`")
        allowed_values = ["reservation", "reservation_release", "reservation_termination", "package_creation", "package_renewal", "package_termination"]
        if reason not in allowed_values:
            raise ValueError(
                "Invalid value for `reason` ({0}), must be one of {1}"
                .format(reason, allowed_values)
            )

        self._reason = reason