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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 exist_edge(self, graph, orig, dest, idx, branch, turn, tick, extant):
 """Declare whether or not this edge exists."""

        if (branch, turn, tick) in self._btts:
            raise TimeError
        self._btts.add((branch, turn, tick))
        graph, orig, dest = map(self.pack, (graph, orig, dest))
        self._edges2set.append((graph, orig, dest, idx, branch, turn, tick, extant))