ERROR: theme: Cannot find template base_helper.tmpl in the lookup

[davidtbo]

Environment

Python version:
3.10.12

Nikola version:
8.3.1

Operating System:
Ubuntu 22.04

Description:

While following the instructions to create a theme, when I run the command:

nikola theme -c base_helper.tmpl

I get the error:
ERROR: theme: Cannot find template base_helper.tmpl in the lookup

Any advice would be appreciated. I was all happy to discover Nikola but was immediately stymied. I'm hoping to get unblocked and start enjoying Nikola :)