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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.
No, that's not the problem. The problem is that you're mutating the input, and that skews the tests. I'll raise this as a new issue.
This comment is hidden because it contains spoiler information about the solution
There must be a problem in you code. You can post it below inside three backticks and make sure to mark as a spoiler.
you're not missing anything - the correct answer is 'bl' which I tested in python.
Are you sure that you are returning the right thing?
Which language are you using?