ping [timestamp]
            Ping the Varnish cache process, keeping the connection alive.

def ping(self, timestamp=None):
        """
        ping [timestamp]
            Ping the Varnish cache process, keeping the connection alive.
        """
        cmd = 'ping'
        if timestamp: cmd += ' %s' % timestamp
        return tuple(map(float, self.fetch(cmd)[1].split()[1:]))