Just a simple feature request but can the UPCA class include the option to add guardbars similar to how EAN8-13-14 support it? Current UPCA barcode via python-barcode:  Requested format: 
Just a simple feature request but can the UPCA class include the option to add guardbars similar to how EAN8-13-14 support it?
Current UPCA barcode via python-barcode:
Requested format:
