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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.
we can do this in order not to modify the source
https://www.codewars.com/kata/reviews/56f69aca9b659001c4000090/groups/590c8d0cda4efbf83b000da7
ES2015 version of the most cleaver solution IMO