使用QCPItemTracer在QCustomPlot中显示点

I am trying for a longer while now to create a mechanism that would create text labels next to my points on a plot with the coordinates. From the documentation, I have read that I need to use QCPItemTracer for that. No matter how i try, I cannot display any additional items on my plot using this object. In the QCustomPlot examples, there is one program that user QCPItemTracer, but when i run it, I also dont see any additional objects. I am trying to run the example code from bellow:I am trying for a longer while now to create a