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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 sort(self, callback=None):
 """ Sort through each item with a callback. :param callback: The callback :type callback: callable or None :rtype: Collection """

        items = self.items

        if callback:
            return self.__class__(sorted(items, key=callback))
        else:
            return self.__class__(sorted(items))