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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def searchitem(self, item, threshold=None):
 """Search the index for items whose key exceeds the threshold similarity to the key of the given item. :return: list of pairs of (item, similarity) by decreasing similarity. [((0, 'SPAM'), 0.375), ((1, 'SPAN'), 0.375)] """

        return self.search(self.key(item), threshold)