def update(self, iterable):
for pair in pairwise_longest(iterable, fillvalue=_FILL):<EOL><INDENT>self._edges.append(pair)<EOL>self._results = None<EOL><DEDENT>
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).