Theme UI themeProvider UUID

Reading through the documentation it's not clear how the themeProvider is getting the UUID generated.

>The Wizard also creates a themeProvider declaration in the <extensions> section of the plugin’s plugin.xml file. This declaration binds the Theme description file to a theme provider extension id.

I am extending an existing pluggin that contains many color schemes and generating a relevant theme json file, but I can't quite tell how this UUID is generated in the plugin.xml. Is it just a random UUID?