Css parser usage.

So I am currently trying to implement nested media CSS styles and seems to not work via string. I'm just struggling to understand how to use this plugin correctly. There is no documentation on how to use it properly and just a bit confused. See i can manage to also parse some of the custom CSS to an array but then there also seems to be no option to add the cssRules via an array? please help me with how to properly import CSS Rules with this tool. Thanks!