code: private Map<String, Object> mapFields(E logEvent) {
          Map<String, Object> map = new HashMap<String, Object>();
  
          map.put("host", host);
  
          map.put("full_message", fullMessageLayout.doLayout(logEvent));
          map.put("short_message", shortMessageLayout.doLayout(logEvent));
  
          stackTraceField(map, logEvent);
  
          map.put("timestamp", logEvent.getTimeStamp() / 1000.0);
  
          map.put("version", "1.1");
  
          map.put("level", LevelToSyslogSeverity.convert(logEvent));
  
          additionalFields(map, logEvent);
  
          staticAdditionalFields(map);
  
          return map;
      }
docs: Creates a map of properties that represent the GELF message.
  
  @param logEvent The log event
  @return map of gelf properties