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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 _data_graph_add_edge(self, src, dst, **edge_labels):
 """ Add an edge in the data dependence graph. :param ProgramVariable src: Source node. :param ProgramVariable dst: Destination node. :param edge_labels: All labels associated with the edge. :return: None """


        if src in self._data_graph and dst in self._data_graph[src]:
            return

        self._data_graph.add_edge(src, dst, **edge_labels)

        self._simplified_data_graph = None