private static void setVersionsToNull(Statement stat) {
    if (stat.getExprents() == null) {
      for (Object obj : stat.getSequentialObjects()) {
        if (obj instanceof Statement) {
          setVersionsToNull((Statement)obj);
        }
        else if (obj instanceof Exprent) {
          setExprentVersionsToNull((Exprent)obj);
        }
      }
    }
    else {
      for (Exprent exprent : stat.getExprents()) {
        setExprentVersionsToNull(exprent);
      }
    }
  }
private static void setVersionsToNull(Statement stat)