code: def export_fem(self, arms=None, format='json', df_kwargs=None):
          
          ret_format = format
          if format == 'df':
              from pandas import read_csv
              ret_format = 'csv'
          pl = self.__basepl('formEventMapping', format=ret_format)
          to_add = [arms]
          str_add = ['arms']
          for key, data in zip(str_add, to_add):
              if data:
                  pl[key] = ','.join(data)
          response, _ = self._call_api(pl, 'exp_fem')
          if format in ('json', 'csv', 'xml'):
              return response
          elif format == 'df':
              if not df_kwargs:
                  return read_csv(StringIO(response))
              else:
                  return read_csv(StringIO(response), **df_kwargs)
docs: Export the project's form to event mapping
  
          Parameters
          ----------
          arms : list
              Limit exported form event mappings to these arm numbers
          format : (``'json'``), ``'csv'``, ``'xml'``
              Return the form event mappings in native objects,
              csv or xml, ``'df''`` will return a ``pandas.DataFrame``
          df_kwargs : dict
              Passed to pandas.read_csv to control construction of
              returned DataFrame
  
          Returns
          -------
          fem : list, str, ``pandas.DataFrame``
              form-event mapping for the project