I do basic python programming and now I want to get deep into language features. I have collected/considered the following to be advanced python capabilities and learning them now. 

Decorator
Iterator
Generator
Meta Class

Anything else to be added/considered to the above list?
I think you'll find that there isn't a good answer to your question.  What's great about Python is that all of its features are fairly easy to understand.  But there's enough stuff in the language and the library that you never get around to learning it all.  So it really boils down to which you've had occasion to use, and which you've only heard about.
If you haven't used decorators or generators, they sound advanced.  But once you actually have to use them in a real-world situation, you'll realize that they're really quite simple, and wonder how you managed to live without them before.
What are features considerd as advanced python?