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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.
...and further simplified to:
| None -> [];)Very nice kata!!
Description, rules, and examples are well written and easy to understand.
There are many test cases (when you hit submit), which have a good decription what are they testing and where's your error if there is one.