What's wrong with this program?

Question

This code is for the final Project in Data Science- (Pandas Pandas Pandas)
https://code.sololearn.com/c8DKMv2ZnIj1/?ref=app
This passes every test except test3.
I have gone through a different code which passes the tests here
https://code.sololearn.com/cA18A6a7a205/?ref=app
But I still can't figure out how differently this code works than mine, and what's missing from my code.

Answer 1

Maybe a bug. Report to support team