public ReservedInstance withBillingSubscriptionId(Long billingSubscriptionId) {
        setBillingSubscriptionId(billingSubscriptionId);
        return this;
    }
<p>
The unique identifier of the billing subscription.
</p>

@param billingSubscriptionId
       The unique identifier of the billing subscription.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-opensearch/src/main/java/com/amazonaws/services/opensearch/model/ReservedInstance.java