While this commit supposedly fixing a typo, this left format_nat_rule undefined
vyos@vyos:~$ sho nat destination rules Traceback (most recent call last): File "/usr/libexec/vyos/op_mode/show_nat_rules.py", line 37, in <module> print(format_nat_rule.format("Rule", "Source" if args.source else "Destination", "Translation", "Outbound Interface" if args.source else "Inbound Interface")) NameError: name 'format_nat_rule' is not defined