code: function mapHeader (h) {
      if (h === undefined) return undefined;
  
      return {
        test: toBoolean(getElementText(h, 'Test', mes)),
        id: getElementText(h, 'ID', mes),
        prepared: getElementText(h, 'Prepared', mes),
        sender: mapParty(_getFirstChildNS(h, 'Sender', mes)),
        receiver: mapParty(_getFirstChildNS(h, 'Receiver', mes))
      };
    }
docs: ------------------------------------------------------------------------------ Functions for mapping the header information (only for structure messages)