: attr
      Returns the name attributes. Each name attribute is a symbol
      capitalized by String#capitalize, such as :Noselect (not :NoSelect).

: attr
      Returns a hash. Each key is one of "MESSAGES", "RECENT", "UIDNEXT",
      "UIDVALIDITY", "UNSEEN". Each value is a number.

: attr
      Returns a hash. Each key is a data item name, and each value is
      its value.

      The current data items are:

      : BODY
          A form of BODYSTRUCTURE without extension data.
      : BODY[<section>]<<origin_octet>>
          A string expressing the body contents of the specified section.
      : BODYSTRUCTURE
          An object that describes the imap.rb"/[MIME-IMB] body structure of a message.
          See imap.rb"/Net::IMAP::BodyTypeBasic, imap.rb"/Net::IMAP::BodyTypeText,
          imap.rb"/Net::IMAP::BodyTypeMessage, imap.rb"/Net::IMAP::BodyTypeMultipart.
      : ENVELOPE
          A imap.rb"/Net::IMAP::Envelope object that describes the envelope
          structure of a message.
      : FLAGS
          A array of flag symbols that are set for this message. flag symbols
          are capitalized by String#capitalize.
      : INTERNALDATE
          A string representing the internal date of the message.
      : RFC822
          Equivalent to BODY[].
      : RFC822.HEADER
          Equivalent to BODY.PEEK[HEADER].
      : RFC822.SIZE
          A number expressing the imap.rb"/[RFC-822] size of the message.
      : RFC822.TEXT
          Equivalent to BODY[TEXT].
      : UID
          A number expressing the unique identifier of the message.

