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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.
The code has for in, but as a comment, that's why it still passes the test.
The author of kata probably added the check after people started solving kata the wrong way, before that it was possible to not add for. However, the solution would still get invalidated if the kata tests changed. No idea how it's still there honestly.
it should use for in to pass this kata