An oracle that gives you a predicted "source language" for every node in a DOM, which is used when converting the result back to the source language during round-tripping.

This code is unique to Parsoid; the PHP implementation does not round-trip. Do not confuse this with PHP's (soon to be deprecated) method LanguageConverter::guessVariant(), which is a heuristic used to disable language conversion when the text is guessed to be already in the desired variant.