'List a subset of the subscribed available mailboxes
This command is allowed in the Authenticated and Selected states.
The parameters and returned object are the same as for the L{list}
method, with one slight difference: Only mailboxes which have been
subscribed can be included in the resulting list.'

def lsub(self, reference, wildcard):

    cmd = 'LSUB'
    args = ('"%s"    "%s"' % (reference, wildcard.encode('imap4-utf-7')))
    resp = ('LSUB',)
    d = self.sendCommand(Command(cmd, args, wantResponse=resp))
    d.addCallback(self.__cbList, 'LSUB')
    return d
