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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.
For 1 hour into regex, you're pretty close to the right one. This site can be useful: https://regex101.com/
Not a kata issue, your regex fails tests like this one:
And because it's failing random tests, the number of tests it fails is random too.