upgradeDowngradeDetails property Null safety

GoogleCloudPaymentsResellerSubscriptionV1SubscriptionUpgradeDowngradeDetails? upgradeDowngradeDetails
read / write

Details about the previous subscription that this new subscription upgrades/downgrades from.

Only populated if this subscription is an upgrade/downgrade from another subscription.

Optional.

Implementation

GoogleCloudPaymentsResellerSubscriptionV1SubscriptionUpgradeDowngradeDetails?
    upgradeDowngradeDetails;