static CloseableItIt<T3<Int, S, S>> tatoeba_parseSentencesCSV(File f) {
  ret mapI_notNulls_closeable(
    linesFromFile(f),
    s -> {
      LS l = splitAtTab(s);
      ret l(l) != 3 ? null : t3(
        parseInt(first(l)), // sentence ID
        intern(second(l)),  // language name, e.g. "deu" or "eng"
        third(l)            // the sentence
      );
    }
  );
}