docs: 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')