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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 update(self, iterable):
 """Update with an ordered iterable of items. Args: iterable: An ordered iterable of items. The relative order of the items in this iterable will be respected in the TopoSet (in the absence of cycles). """

        for pair in pairwise_longest(iterable, fillvalue=_FILL):
            self._edges.append(pair)
            self._results = None