def version(self):
        """
        Get the version of the server.

        @return: a deferred that will fire with the string value of the
            version.
        @rtype: L{Deferred}
        """
        if self._disconnected:
            return fail(RuntimeError("not connected"))
        self.sendLine(b"version")
        cmdObj = Command(b"version")
        self._current.append(cmdObj)
        return cmdObj._deferred

        Get the version of the server.

        @return: a deferred that will fire with the string value of the
            version.
        @rtype: L{Deferred}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/memcache.py