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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.
good solution, but it doesn't check for alpha, now we can pass not only letters!
For example this call in this solution
findMissingLetter(['<','>'])return us'='which is not a letter actually