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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 _add_edge(self, source, target, **kwargs):
 """Add an edge to the graph."""

        # Start with default edge properties
        edge_properties = self.edge_properties
        # Overwrite ones that are given in function call explicitly
        for k, v in kwargs.items():
            edge_properties[k] = v
        self.graph.add_edge(source, target, **edge_properties)