'Flush all cached values.
@return: a deferred that will be called back with C{True} when the
operation has succeeded.
@rtype: L{Deferred}'

def flushAll(self):

    if self._disconnected:
        return fail(RuntimeError('not    connected'))
    self.sendLine('flush_all')
    cmdObj = Command('flush_all')
    self._current.append(cmdObj)
    return cmdObj._deferred
