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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.
Duplicate issue below
The test case expected and actual results are still swapped for the null str test case.
The case will pass as long as you make sure that you return an empty string if str is null.
Not sure if the author fixed it, but the tests work fine for me now