code: func (d *dataEncoder) modeIndicator(dataMode dataMode) *bitset.Bitset {
  	switch dataMode {
  	case dataModeNumeric:
  		return d.numericModeIndicator
  	case dataModeAlphanumeric:
  		return d.alphanumericModeIndicator
  	case dataModeByte:
  		return d.byteModeIndicator
  	default:
  		log.Panic("Unknown data mode")
  	}
  
  	return nil
  }
docs: // modeIndicator returns the segment header bits for a segment of type dataMode.