Variable Value Callback

[mattiacorpora]

Hello,
I'm new to using asyncua and I'm finding it quite comprehensive. I have a question regarding variable handling with callbacks. I'm interested in understanding how to set up callbacks for both reading and writing variables in asyncua.
Specifically, I would like to ensure that on the server side, every time a client reads a variable, a callback is triggered before the read operation, and another callback is activated after a write operation.
Could you please provide guidance or examples on how to achieve this using asyncua?
Thank you for your assistance.