I would like to give some feedback about COMMON WORDS SOLVE

From: https://checkio.org/mission/common-words/solve/

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Though the folloing code works in the try section and in local PYthn the console throughs an error saying SET is not a date type

def checkio(first, second): a = first.split(",") b = second.split(",") a1 = set(a) b1 = set(b) result = a1.intersection(b1) return result