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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 to_dataframe(self, extra_edges_columns=[]):
 """ Return this network in pandas DataFrame. :return: Network as DataFrame. This is equivalent to SIF. """

        return df_util.to_dataframe(
            self.session.get(self.__url).json(),
            edges_attr_cols=extra_edges_columns
        )