Thank you, Steven.
On https://github.com/jeremyBass/connections-levels/blob/master/connections-levels/includes/class-connections-levels.php I see a large block of PHP code, including the four lines you specifically called attention to.
However, I don’t see a link to download the plugin.
How do I download the plugin – or what do I do with this block of code? Is there some place I should insert it?