docs: public void update(Transaction xaction, T item, Map<String,Object> state) throws PersistenceException {
          if( update == null ) {
              synchronized( this ) {
                  while( update == null ) {
                      compileUpdater();
                      try { wait(1000L); }
                      catch( InterruptedException ignore ) { /* ignore this */ }
                  }
              }
          }        
          state.put("--key--", getKey());
          xaction.execute(update, state);
          if( dependency != null ) {
              dependency.updateDependencies(xaction, item, state);
          }
      }