code: def save_json(self, fname_prefix='model'):
          
          cyjs_str = self.print_cyjs_graph()
          # outputs the graph
          with open(fname_prefix + '.json', 'wb') as fh:
              fh.write(cyjs_str.encode('utf-8'))
          # outputs the context of graph nodes
          context_str = self.print_cyjs_context()
          with open(fname_prefix + '_context.json', 'wb') as fh:
              fh.write(context_str.encode('utf-8'))
docs: Save the assembled Cytoscape JS network in a json file.
  
          This method saves two files based on the file name prefix given.
          It saves one json file with the graph itself, and another json
          file with the context.
  
          Parameters
          ----------
          fname_prefix : Optional[str]
              The prefix of the files to save the Cytoscape JS network and
              context to.
              Default: model