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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
If the input is an empty list, the code inside your loop won't ever be reached, that's why.
Your solution function is wrong, because it does not return any value.
Please see if this helps: https://docs.codewars.com/training/troubleshooting#expected-the-same
Not a kata issue, its a bug in user solution.