Creating new Operation Advisor (Pre Condition)

Hi
I need to create new pre-conditions in my RTC, for example that some specific child must be closed in certain state.

I have made a little research about this and found some articles in the jazz.net library and the wiki.

I have read the "Creating Custom Operation Advisors" https://jazz.net/library/article/495
And I understand how to install the SDK, the plug-in but what I need to know is how to set up code.
How to get the state of the workitem, the childs it has, the state of thos childs , etc.

Someone can helpme with the code please?

Thanks!