private void ensureDataDisksIsMutable() {
      if (!((bitField0_ & 0x00040000) != 0)) {
        dataDisks_ = new java.util.ArrayList<com.google.cloud.tpu.v2.AttachedDisk>(dataDisks_);
        bitField0_ |= 0x00040000;
      }
    }
<pre>
Output only. The unique identifier for the TPU Node.
</pre>

<code>int64 id = 33 [(.google.api.field_behavior) = OUTPUT_ONLY];</code>

@return This builder for chaining.
java-tpu/proto-google-cloud-tpu-v2/src/main/java/com/google/cloud/tpu/v2/Node.java