docs: def getmessage(self) -> str:
          """ parse self into unicode string as message content """   
          image = {}
          for key, default in vars(self.__class__).items():
              if not key.startswith('_') and key !='' and (not key in vars(QueueMessage).items()):                                      
                  if isinstance(default, datetime.date):
                      image[key] = safe_cast(getattr(self, key, default), str, dformat=self._dateformat)
                  if isinstance(default, datetime.datetime):
                      image[key] = safe_cast(getattr(self, key, default), str, dformat=self._datetimeformat)
                  else:
                      image[key] = getattr(self, key, default)                              
          return str(image)