 * MimeTreeParser::MessagePartList
  * MimeTreeParser::MessagePartList
   * MimeTreeParser::MimeMessagePart
    * MimeTreeParser::TextMessagePart
     * MimeTreeParser::MessagePart
   * MimeTreeParser::MimeMessagePart
    * MimeTreeParser::EncapsulatedRfc822MessagePart
     * MimeTreeParser::SignedMessagePart
      * MimeTreeParser::TextMessagePart
       * MimeTreeParser::MessagePart
   * MimeTreeParser::MimeMessagePart
    * MimeTreeParser::TextMessagePart
     * MimeTreeParser::MessagePart
