private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.tpu.v2alpha1.BootDiskConfig,
            com.google.cloud.tpu.v2alpha1.BootDiskConfig.Builder,
            com.google.cloud.tpu.v2alpha1.BootDiskConfigOrBuilder>
        getBootDiskConfigFieldBuilder() {
      if (bootDiskConfigBuilder_ == null) {
        bootDiskConfigBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.tpu.v2alpha1.BootDiskConfig,
                com.google.cloud.tpu.v2alpha1.BootDiskConfig.Builder,
                com.google.cloud.tpu.v2alpha1.BootDiskConfigOrBuilder>(
                getBootDiskConfig(), getParentForChildren(), isClean());
        bootDiskConfig_ = null;
      }
      return bootDiskConfigBuilder_;
    }
<pre>
Optional. Boot disk configuration.
</pre>

<code>
.google.cloud.tpu.v2alpha1.BootDiskConfig boot_disk_config = 49 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-tpu/proto-google-cloud-tpu-v2alpha1/src/main/java/com/google/cloud/tpu/v2alpha1/Node.java