Some examples or readme about preprocess?

[hbxxxdq]

Hello, I just recently started working with python code a few days and there is some code that I can't easily understand, so I was wondering if you could give an example of how to use CSV to PKL. I looked at the preprocess code, but it keeps running with errors and I don't know what's wrong. Another question is if you can provide a sample of the format of the metadata.json. Thank you very much!