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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.
i missed the 0 case from the rules. My bad.
0 is not a natural number; however, it's one of the test cases.
'is' is not the same as '=='. Sorry.
is operator checks for object identity. I don't think coupons with same code value should be guarnteed to be identical objects. Thus, the fact that 'is' works is just luck -- the tester passes same objects, that's all