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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.
After I submitted my solution,I got the message:'TypeError: Object 1 has no method 'slice' at groupByCommas'
However,it was no problem when I ran code at local environment,and the result satisfied all the conditions of the cases that author offered.I have no idea about this message,who can help me???