docs: static protected void addCodecOnly(CombinedRegistry registry, String name, ChannelHandler codec){
  		Object oldValue = registry.lookup(name);
  		if (oldValue != null && oldValue != codec){
  			throw new IllegalArgumentException("Codec name '" + name + "' is already in use in at least one of the registries.");
  		}
  		registry.getDefaultSimpleRegistry().put(name, codec);
  	}