If you didn't configure DNS forwarding and try to show statistics, this will result in an error.
sever@vyos-1.3-bgp:~$ show dns forwarding statistics
Traceback (most recent call last):
File "/usr/libexec/vyos/op_mode/dns_forwarding_statistics.py", line 7, in <module>
from vyos.config import cmd
ImportError: cannot import name 'cmd' from 'vyos.config' (/usr/lib/python3/dist-packages/vyos/config.py)
sever@vyos-1.3-bgp:~$