code: def save_dot(self, file_name='graph.dot'):
          
          s = self.get_string()
          with open(file_name, 'wt') as fh:
              fh.write(s)
docs: Save the graph in a graphviz dot file.
  
          Parameters
          ----------
          file_name : Optional[str]
              The name of the file to save the graph dot string to.