How to use the uritemplate.orderedset.Link function in uritemplate

def __init__(self, iterable=None):
        self.__root = root = Link()  # sentinel node for doubly linked list
        root.prev = root.next = root
        self.__map = {}  # key --> link
        if iterable is not None:
            self |= iterable

def add(self, key):
        # Store new key in a new link at the end of the linked list
        if key not in self.__map:
            self.__map[key] = link = Link()
            root = self.__root
            last = root.prev
            link.prev, link.next, link.key = last, root, key
            last.next = root.prev = proxy(link)