/**
* Serializes blip into Message.
*/
private WalkaroundDocumentSnapshot toProtoBuf(BlipDataImpl blip) {
WalkaroundDocumentSnapshot document = MessageFactoryHelper.createDocumentSnapshot();
document.setDocumentId(blip.getId());
document.setAuthor(blip.getAuthor().getAddress());
document.setLastModifiedTime(blip.getLastModifiedTime());
document.setLastModifiedVersion(blip.getLastModifiedVersion());
document.addAllContributor(listOfParticipantAddresses(blip.getContributors()));
ProtocolDocumentOperation documentOperation =
OperationSerializer.createMutationOp(blip.getContent().asOperation());
document.setContent(documentOperation);
return document;
}