Final Cut Pro Workflow Extension - Access FCPXSequence data

Hi,

I’m trying to make a very simple Workflow Extension for Final Cut Pro.

No problem to access timeline objects from the code below :

host = ProExtensionHostSingleton() as? FCPXHost
let timeline = host.timeline

But how to access data from other proxy objects like FCPXProject or FCPXSequence ?

If someone can give me an example or a little advice on how to use it, that would be really helpful.

Thanks