code: private boolean cacheComplete() {
        final boolean complete;
        if (m_cache != null) {
            complete = m_cache.isComplete();
        } else {
            complete = false;
        }
        return complete;
    }
docs: If this NodeSequence has a cache, and that cache is
  fully populated then this method returns true, otherwise
  if there is no cache or it is not complete it returns false.