How do you do a modular (multi-file) Python development strategy and how do you do it online?

1. I love FMZ's online review, it's simple and intuitive, but lately it's become more and more complicated to write the policy, and it's impossible to put all the files in one file (more than 1.5K lines of code), so I'm doing modular writing, but how do I use online review?

2. How do you refer to a third-party Python library or a library you write yourself?

3. How do you perform file IO operations, such as reading and writing files?

I'm just coming to the FMZ platform soon, hopefully all roads will be cleared.