docs: def flatten_tree_to_ident_hashes(item_or_tree,
                                   lucent_id=TRANSLUCENT_BINDER_ID):
      """Flatten a tree to id and version values (ident_hash)."""
      if 'contents' in item_or_tree:
          tree = item_or_tree
          if tree['id'] != lucent_id:
              yield tree['id']
          for i in tree['contents']:
              # yield from flatten_tree_to_ident_hashs(i, lucent_id)
              for x in flatten_tree_to_ident_hashes(i, lucent_id):
                  yield x
      else:
          item = item_or_tree
          yield item['id']