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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.
One of the input tests passes the sum_array() function None. You need to check for (and handle) a None input before attempting to feed it to len() or sorted().
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