private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.tpu.v2alpha1.UpcomingMaintenance,
            com.google.cloud.tpu.v2alpha1.UpcomingMaintenance.Builder,
            com.google.cloud.tpu.v2alpha1.UpcomingMaintenanceOrBuilder>
        getUpcomingMaintenanceFieldBuilder() {
      if (upcomingMaintenanceBuilder_ == null) {
        upcomingMaintenanceBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.tpu.v2alpha1.UpcomingMaintenance,
                com.google.cloud.tpu.v2alpha1.UpcomingMaintenance.Builder,
                com.google.cloud.tpu.v2alpha1.UpcomingMaintenanceOrBuilder>(
                getUpcomingMaintenance(), getParentForChildren(), isClean());
        upcomingMaintenance_ = null;
      }
      return upcomingMaintenanceBuilder_;
    }
<pre>
Output only. Upcoming maintenance on this TPU node.
</pre>

<code>
.google.cloud.tpu.v2alpha1.UpcomingMaintenance upcoming_maintenance = 51 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-tpu/proto-google-cloud-tpu-v2alpha1/src/main/java/com/google/cloud/tpu/v2alpha1/Node.java