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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.
Since you know that there will be exactly 1 unique string in the entire array, you can identify the common strings by looking at either 2 indexes (best case scenario) or 3 (worst case). All you need is two strings to match to confirm it.
The python test cases are incomplete. It is easy to pass this if you assume that the first element is never going to be the unique one. The test suite needs to have cases where every index at some point contains the unique string.
Should have more tests, you can pass this by hardcoding answers.
Very disappointed by the omission of the Oxford comma.