@java.lang.Override
  public Builder toBuilder() {
    return this == DEFAULT_INSTANCE ? new Builder() : new Builder().mergeFrom(this);
  }
<pre>
Optional. Idempotent request UUID.
</pre>

<code>string request_id = 4 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The bytes for requestId.
java-tpu/proto-google-cloud-tpu-v2/src/main/java/com/google/cloud/tpu/v2/CreateQueuedResourceRequest.java