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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.
The format the test uses is:
Sudoku(data).is_valid()
Your function returns a boolean, so the equivalent to this ends up happening:
result = Sudoku(data) # You return a boolean
if result.is_valid(): ... # AttributeError
If you are dead set on using a function, you need to make sure it returns some kind of object with a method called is_valid() that returns the result. Hint: try using collections.namedtuple
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