code: def _iris_cell_methods_to_str(cell_methods_obj):
      
      cell_methods = []
      for cell_method in cell_methods_obj:
          names = ''.join(['{}: '.format(n) for n in cell_method.coord_names])
          intervals = ' '.join(['interval: {}'.format(interval)
                                for interval in cell_method.intervals])
          comments = ' '.join(['comment: {}'.format(comment)
                               for comment in cell_method.comments])
          extra = ' '.join([intervals, comments]).strip()
          if extra:
              extra = ' ({})'.format(extra)
          cell_methods.append(names + cell_method.method + extra)
      return ' '.join(cell_methods)
docs: Converts a Iris cell methods into a string