error when running main.py in prepare_data

Hi,

I've been following the instructions to prepare PDB data as indicated in the README.md in rnaglib/rnaglib/prepare_data and I've been running into a few errors:

1. for main.py and the first example I was trying to run from rnaglib, I was denied access when trying to run the scripts and have to run the chmod command to get permission to access the files
2. once this is done, the files are not executable as python files on my machine and I have to shebang them to get them to recognize the import statements being used. But once I do this it seems like things work.
3. when running main.py in prepare_data, I keep running into two problems: either the options mentioned in the README.md and in the argparser in the main.py file are not recognized:

or I get the following error message:

I'm running on IOS with Python 3.8.8

Thank you, Séraphin