Using FreeMarker extension points

Hi,

I'm writing a plugin which needs to contribute implicit variables to FreeMarker templates. I've found the 'FtlGlobalVariableProvider' class which can be extended and registered under the 'freemarker.globalVariableProvider' extension point.

But I'm not sure how to create the FtlXXX variables. I've tried this:

    @NotNull
    @Override
    public List<? extends FtlVariable> getGlobalVariables( FtlFile ftlFile )
    {
        FtlImplicitVariable languages = new FtlImplicitVariable( null, "languages", ftlFile );
        languages.addSubVariable( "en" );
        return Arrays.asList( languages );
    }