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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 set(self, path, item, replace):
 """ Sets item for `path` and returns the item. Replaces existing item with `item` when `replace` is true :param path: Path for item :param item: New item :param replace: Updating mode :type path: list :type item: object :type replace: bool """

        if len(path) == 0:
            if self._item is None or replace:
                self._item = item

            return self._item

        else:
            head, tail = path[0], path[1:]

            if head.startswith(':'):
                default = (head[1:], self.__class__())
                _, rtree = self._subtrees.setdefault(self._WILDCARD, default)
                return rtree.set(tail, item, replace)

            else:
                rtree = self._subtrees.setdefault(head, self.__class__())
                return rtree.set(tail, item, replace)