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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 traverse(self, edge):
 """ Traverse the graph, and selecting the destination nodes for a particular relation that the selected nodes are a source of, i.e. select the friends of my friends. You can traverse indefinitely. :param edge: The edge query. If the edge's destination node is specified then the source nodes will be selected. """

        query = self.statement
        rel, dst = edge.rel, edge.dst
        statement, params = (
            SQL.compound_fwd_query(query, rel) if dst is None else
            SQL.compound_inv_query(query, rel, dst)
        )
        return self.derived(statement, params, replace=True)