Under "Displaying a Rating Using a Template Parameter" it says "For the form field defined in the example above...". What form field in what example? I think perhaps that text has been deleted.
Topic on Extension talk:Semantic Rating/Flow
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In fact, it specifically states that it has been removed: "Removed form input, since it is now part of the Page Forms extension." You need to update your example.
Thanks for noticing that. It is now fixed.