I have also written a little Rpi4B Thonny python 3.7.3 function to do reader.write(...) and reader.read() and got the same results as using CLI terminal commands as shown in my old answer. I know you are are Circuit python. Perhaps you can try your luck with circuit python. Good luck and cheers.
I have tidied up my little program: penzu.com/p/f77f0034. (Ref 9 of my answer's reference list). It is a copy/paste/run program, with sample output. You might like to try it and let me know any problems. Nothing urgent though. Have a nice weekend.