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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.
The reference solution was wrong. Fixed it, try again.
Sorry I must mention, submitting it as final works, but the test cases fail.
Issue with Ruby. It says in the description to return 0 if there is nothing to sum. One test case fails for me because it says it expects nil to return when there is nothing to sum so I am unable to complete this.