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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.
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I believe this is still should be worded better.
Saying "If arr contains neither 5 nor 13" implies you're looking for the case where there is no 5, as well as no 13 (both have to not exist). What the white array is really testing for is a case where there is either no 5 or no 13 (only one of those does not exist).
Perhaps you could say "If arr either does not contain 5, or it does not contain 13, we should return "It's a white array".
There is an issue with tests 6, 7, and 8 as they will not pass. I tried multiple variations of the solution as well as an inverse solution with same result. All random tests pass for me.