code: function serializeEntry(entry) {
      return {
          id: entry.id,
          remote_id: entry.remote ? entry.remote.getId() : undefined,
          matrix_id: entry.matrix ? entry.matrix.getId() : undefined,
          remote: entry.remote ? entry.remote.serialize() : undefined,
          matrix: entry.matrix ? entry.matrix.serialize() : undefined,
          data: entry.data
      }
  }
docs: not a member function so callers can provide a POJO