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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.
more clean I think than using combination of filter/sum
Here you've just travel the list one time
a more generic solution is better
passing test but not a good solution