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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 freefn(self, item, fn, at_tail):
 """ Set a free function for the specified list item. When the item is destroyed, the free function, if any, is called on that item. Use this when list items are dynamically allocated, to ensure that you don't have memory leaks. You can pass 'free' or NULL as a free_fn. Returns the item, or NULL if there is no such item. """

        return c_void_p(lib.zlist_freefn(self._as_parameter_, item, fn, at_tail))