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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 _rfind(lst, item):
 """ Reverse look-up. :param list lst: The list to look up in. :param item: The item to look for. :return: Offset of the item if found. A ValueError is raised if the item is not in the list. :rtype: int """


        try:
            return dropwhile(lambda x: lst[x] != item,
                             next(reversed(range(len(lst)))))
        except Exception:
            raise ValueError("%s not in the list" % item)