code: func (f LogstashFormatter) Format(e *logrus.Entry) ([]byte, error) {
  	ne := copyEntry(e, f.Fields)
  	dataBytes, err := f.Formatter.Format(ne)
  	releaseEntry(ne)
  	return dataBytes, err
  }
docs: // Format formats an entry to a Logstash format according to the given Formatter and Fields.
  //
  // Note: the given entry is copied and not changed during the formatting process.