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 โ€œWorld Wide Webโ€ and โ€œgetโ€. 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.