'Return the connection to the Authenticated state.
This command is allowed in the Selected state.
Issuing this command will also remove all messages flagged \Deleted
from the selected mailbox if it is opened in read-write mode,
otherwise it indicates success by no messages are removed.
@rtype: C{Deferred}
@return: A deferred whose callback is invoked when the command
completes successfully or whose errback is invoked if it fails.'

def close(self):

    return self.sendCommand(Command('CLOSE'))
