Folder Objects
--------------
`Folder' instances represent open folders and have the following
methods:
`error(format[, ...])'
Print an error message - can be overridden.
`getfullname()'
Return the folder's full pathname.
`getsequencesfilename()'
Return the full pathname of the folder's sequences file.
`getmessagefilename(n)'
Return the full pathname of message N of the folder.
`listmessages()'
Return a list of messages in the folder (as numbers).
`getcurrent()'
Return the current message number.
`setcurrent(n)'
Set the current message number to N.
`parsesequence(seq)'
Parse msgs syntax into list of messages.
`getlast()'
Get last message, or `0' if no messages are in the folder.
`setlast(n)'
Set last message (internal use only).
`getsequences()'
Return dictionary of sequences in folder. The sequence names are
used as keys, and the values are the lists of message numbers in
the sequences.
`putsequences(dict)'
Return dictionary of sequences in folder {name: list}.
`removemessages(list)'
Remove messages in list from folder.
`refilemessages(list, tofolder)'
Move messages in list to other folder.
`movemessage(n, tofolder, ton)'
Move one message to a given destination in another folder.
`copymessage(n, tofolder, ton)'
Copy one message to a given destination in another folder.