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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 test doesn't say you should care for undefined or null
It is fine! But, it is also good to check input validation. Let's say I call your function with an undefined input or with a non valid input