@java.lang.Override
  public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(eventMessage_)) {
      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, eventMessage_);
    }
    if (((bitField0_ & 0x00000001) != 0)) {
      output.writeMessage(2, getPayload());
    }
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(eventId_)) {
      com.google.protobuf.GeneratedMessageV3.writeString(output, 3, eventId_);
    }
    getUnknownFields().writeTo(output);
  }
<pre>
User defined Event Id, used to classify event, within a delivery interval,
events from the same application instance with the same id will be
de-duplicated &amp; only first one will be sent out. Empty event_id will be
treated as "".
</pre>

<code>string event_id = 3;</code>

@return The bytes for eventId.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/AppPlatformEventBody.java