docs: public List<LexiconEntryInfo> getSpannedLexiconEntries() {
      if (isTerminal()) {
        return Arrays.asList(lexiconEntry);
      } else {
        List<LexiconEntryInfo> lexiconEntries = Lists.newArrayList();
        lexiconEntries.addAll(left.getSpannedLexiconEntries());
        lexiconEntries.addAll(right.getSpannedLexiconEntries());
        return lexiconEntries;
      }
    }