docs: 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)