docs: public Set tokens() {
          if (tokenSet == null) {
              tokenSet = new AbstractSetView() {
                  public long size() {
                      return inMemoryManagedObjects.size();
                  }
  
                  public Iterator iterator() {
                      final java.util.Iterator tokenIterator = inMemoryTokens.values().iterator();
                      return new Iterator() {
  
                          public boolean hasNext()
                          {
                              return tokenIterator.hasNext();
                          } // hasNext().
  
                          public Object next()
                          {
                              return tokenIterator.next();
                          } // next().
  
                          public boolean hasNext(Transaction transaction)
                                          throws ObjectManagerException
                          {
                              throw new UnsupportedOperationException();
                          } // hasNext().
  
                          public Object next(Transaction transaction)
                                          throws ObjectManagerException
                          {
                              throw new UnsupportedOperationException();
                          } // next().
  
                          public Object remove(Transaction transaction)
                                          throws ObjectManagerException
                          {
                              throw new UnsupportedOperationException();
                          } // remove().               
                      }; // new Iterator().
                  } // iterator().  
              }; // new AbstractSetView().
          } // if (tokenSet == null). 
          return tokenSet;
      }