Get server time.
        Optional arguments:
        * target=None - Target server.

def time(self, target=None):
        """
        Get server time.
        Optional arguments:
        * target=None - Target server.
        """
        with self.lock:
            if target:
                self.send('TIME %s' % target)
            else:
                self.send('TIME')
            time = ''
            msg = self._recv(rm_colon=True, expected_replies=('391',))
            if msg[0] == '391':
                time = msg[2].split(':', 1)[1]
            return time