code: void releaseId(Id id) {
  
          Integer pos = idPosMap.get(id);
          if (pos != null) {
              idPosMap.remove(id);
              freePositions.add(pos);
  
              for (HierarchicalTypeStore s : superTypeStores) {
                  s.releaseId(id);
              }
          }
      }
docs: - remove from idPosMap
  - add to freePositions.
  @throws RepositoryException