def enable(self, interface_id, dns_relay_profile=None):
        """
        Enable the DNS Relay service on this engine.

        :param int interface_id: interface id to enable relay
        :param str,DNSRelayProfile dns_relay_profile: DNSRelayProfile element
            or str href
        :raises EngineCommandFailed: interface not found
        :raises ElementNotFound: profile not found
        :return: None
        """
        if not dns_relay_profile:  # Use default
            href = DNSRelayProfile('Cache Only').href
        else:
            href = element_resolver(dns_relay_profile)

        intf = self.engine.interface.get(interface_id)
        
        self.engine.data.update(dns_relay_profile_ref=href)
        self.engine.data.update(dns_relay_interface=intf.ndi_interfaces)
Enable the DNS Relay service on this engine.

        :param int interface_id: interface id to enable relay
        :param str,DNSRelayProfile dns_relay_profile: DNSRelayProfile element
            or str href
        :raises EngineCommandFailed: interface not found
        :raises ElementNotFound: profile not found
        :return: None