Returns an immutable instance of [BillingRetrieveUsageResponse].
public BillingRetrieveUsageResponse build()Returns an immutable instance of [BillingRetrieveUsageResponse]. Further updates to this [Builder] will not mutate the returned instance. The following fields are required:
.billableMetricId()
.billableMetricName()
.customerId()
.endTimestamp()
.groups()
.startTimestamp()
.value()
IllegalStateException: if any required field is unset.