Use wget to download the Python file.

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A short description from Wikipedia: GNU Wget (or just Wget, formerly Geturl, also written as its package name, wget) is a computer program that retrieves content from web servers. It is part of the GNU Project. Its name derives from “World Wide Web” and “get”. It supports downloading via HTTP, HTTPS, and FTP.
man wget
wget https://artifacts.picoctf.net/c/37/serpentine.py
sudo nano serpentine.py

Inspect the source code of the Python file and just in the second if statement add this.

elif choice == 'b':
    print('\nOops! I must have misplaced the print_flag function! Check my source code!\n\n')
    print(f"{print_flag()}")

All the information was there. We just need to print out the flag.