code: def _step99(self, in_row, tmp_row, out_row):
          
          park_info = ''
          for field in self._mandatory_fields:
              if field not in out_row or not out_row[field]:
                  if park_info:
                      park_info += ' '
                  park_info += field
  
          return park_info, None
docs: Validates all mandatory fields are in the output row and are filled.
  
          :param dict in_row: The input row.
          :param dict tmp_row: Not used.
          :param dict out_row: The output row.