'Get some stats from the server. It will be available as a dict.
@param arg: An optional additional string which will be sent along
with the I{stats} command.  The interpretation of this value by
the server is left undefined by the memcache protocol
specification.
@type arg: L{None} or L{bytes}
@return: a deferred that will fire with a L{dict} of the available
statistics.
@rtype: L{Deferred}'

def stats(self, arg=None):

    if arg:
        cmd = ('stats    ' + arg)
    else:
        cmd = 'stats'
    if self._disconnected:
        return fail(RuntimeError('not    connected'))
    self.sendLine(cmd)
    cmdObj = Command('stats', values={})
    self._current.append(cmdObj)
    return cmdObj._deferred
