@java.lang.Override
    public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
        if (!com.google.protobuf.GeneratedMessage.isStringEmpty(participantSid_)) {
            com.google.protobuf.GeneratedMessage.writeString(output, 1, participantSid_);
        }
        if (!payload_.isEmpty()) {
            output.writeBytes(2, payload_);
        }
        for (int i = 0; i < destinationSids_.size(); i++) {
            com.google.protobuf.GeneratedMessage.writeString(output, 3, destinationSids_.getRaw(i));
        }
        if (((bitField0_ & 0x00000001) != 0)) {
            com.google.protobuf.GeneratedMessage.writeString(output, 4, topic_);
        }
        if (!com.google.protobuf.GeneratedMessage.isStringEmpty(participantIdentity_)) {
            com.google.protobuf.GeneratedMessage.writeString(output, 5, participantIdentity_);
        }
        for (int i = 0; i < destinationIdentities_.size(); i++) {
            com.google.protobuf.GeneratedMessage
                    .writeString(output, 6, destinationIdentities_.getRaw(i));
        }
        getUnknownFields().writeTo(output);
    }
<pre>
topic under which the message was published
</pre>

<code>optional string topic = 4;</code>

@return The bytes for topic.
turms-plugins/turms-plugin-livekit/src/main/java/im/turms/plugin/livekit/core/proto/models/UserPacket.java