code: def all_groupings(partition):
      
      if not all(partition):
          raise ValueError('Each part of the partition must have at least one '
                           'element.')
  
      micro_groupings = [_partitions_list(len(part) + 1) if len(part) > 1
                         else [[[0], [1]]] for part in partition]
  
      for grouping in itertools.product(*micro_groupings):
          if all(len(element) < 3 for element in grouping):
              yield tuple(tuple(tuple(tuple(state) for state in states)
                                for states in grouping))
docs: Return all possible groupings of states for a particular coarse graining
      (partition) of a network.
  
      Args:
          partition (tuple[tuple]): A partition of micro-elements into macro
              elements.
  
      Yields:
          tuple[tuple[tuple]]: A grouping of micro-states into macro states of
          system.
  
      TODO: document exactly how to interpret the grouping.