def _setup_qos_extension(self):
        """Setup the QOS extension if it is required."""
        if not CONF.AGENT.enable_qos_extension:
            return
        self._qos_ext = qos_extension.QosAgentExtension()
        self._qos_ext.consume_api(self)
        self._qos_ext.initialize(self._connection, 'hyperv')
Setup the QOS extension if it is required.