code: def to_csv(self, fname_radical, **kwargs):
          
          if self.data is not None:
              self.data.to_csv(fname_radical+'_data.csv', index=False, **kwargs)
              pd.DataFrame(self.adjacency_matrix).to_csv(fname_radical \
                                                         + '_target.csv',
                                                         index=False, **kwargs)
  
          else:
              raise ValueError("Graph has not yet been generated. \
                                Use self.generate() to do so.")
docs: Save data to the csv format by default, in two separate files.
  
          Optional keyword arguments can be passed to pandas.