code: def save_model(self, path, output_format=None):
          
          if output_format == 'pickle':
              pybel.to_pickle(self.model, path)
          else:
              with open(path, 'w') as fh:
                  if output_format == 'json':
                      pybel.to_json_file(self.model, fh)
                  elif output_format == 'cx':
                      pybel.to_cx_file(self.model, fh)
                  else: # output_format == 'bel':
                      pybel.to_bel(self.model, fh)
docs: Save the :class:`pybel.BELGraph` using one of the outputs from
          :py:mod:`pybel`
  
          Parameters
          ----------
          path : str
              The path to output to
          output_format : Optional[str]
              Output format as ``cx``, ``pickle``, ``json`` or defaults to ``bel``