I saw you already solved your own issue. Just want to make sure you understand what the actual issue was and why.
In order to use a function, such as Light(), the interpreter running your script needs to know what that function does. To do that, either you need to have defined it in your code (like you did with your main function) or you need to have imported it from from a another source like lifxlan where it is defined. In your original script, you imported the function LifxLAN, though as you discovered, you forgot to import Light as well.
Additionally, instead of importing each function, you could have also imported the entirety of the lifxlan library by changing your import statement to import lifxlan. I'm not recommending you do that. It's not best practice to import more than you need and it can cause issues if what you're importing is not just a library but also executes code. But, if you did import the whole library, that would have imported all of the functions in lifxlan including both LifexLAN and Light. You could then call those functions by prefixing the library name to the functions. For example, lifxlan.Light().