If you are looking at a new project, I would highly suggest you just don't.
The way you access the serial port is documented here:
I can't stress enough how bad this is. It can be done, and you can also add modules if they were supported in python 2.6/2.7 but again unless you have a fleet of WR31s then don't.
The newer IX10 is a much better proposition which runs linux and more importantly python 3.10 and you have access to the serial port very easily.
What exactly are you trying to do with the serial port?