docs: def fullyflatten(container):
      """
      Completely flattens out a cluster and returns a one-dimensional set
      containing the cluster's items. This is useful in cases where some items of
      the cluster are clusters in their own right and you only want the items.
  
      :param container: the container to flatten.
      """
      flattened_items = []
  
      for item in container:
          if hasattr(item, 'items'):
              flattened_items = flattened_items + fullyflatten(item.items)
          else:
              flattened_items.append(item)
  
      return flattened_items