public string ToString(ParseNode_Root parser)
    {
        var result = new StringBuilder(m_sNtName + " : " + rhs + " .");

        if (FirstSet != null)
        {
            result.Append("\n  lookahead " + FirstSet.ToString(parser));
        }
        if (FollowSet != null)
        {
            result.Append("\n  follow " + FollowSet.ToString(parser));
        }
        return(result.ToString());
    }