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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 stream_interactions(self):
 """Generate a temporal ordered stream of interactions. Returns ------- nd_iter : an iterator The iterator returns a 4-tuples of (node, node, op, timestamp). Examples -------- [(0, 1, '+', 0), (1, 2, '+', 0), (2, 3, '+', 0), (3, 4, '+', 1), (4, 5, '+', 1), (5, 6, '+', 1)] """

        timestamps = sorted(self.time_to_edge.keys())
        for t in timestamps:
            for e in self.time_to_edge[t]:
                yield (e[0], e[1], e[2], t)