public GenericConfigHandle subscribe(ConfigKey<RawConfig> key, List<String> defContent, TimingValues timingValues) {
        checkStateBeforeSubscribe();
        GenericJRTConfigSubscription sub = new GenericJRTConfigSubscription(key, defContent, requester, timingValues);
        GenericConfigHandle handle = new GenericConfigHandle(sub);
        subscribeAndHandleErrors(sub, key, handle, timingValues);
        return handle;
    }
Subscribes to config without using the class. For internal use in config proxy.

@param key the {@link ConfigKey to subscribe to}
@param defContent the config definition content for the config to subscribe to
@param timingValues {@link TimingValues}
@return generic handle
config/src/main/java/com/yahoo/config/subscription/impl/GenericConfigSubscriber.java