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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 edges(self):
 """ Edges of this graph, in canonical order. """

        canonical_edges = set()
        for v1, neighbours in self._vertices.items():
            for v2 in neighbours:
                edge = self.canonical_order((v1, v2))
                canonical_edges.add(edge)
        return canonical_edges