docs: static Matcher combineCharSeqAfterIndexOf(Matcher matcher) {
      if (matcher instanceof IndexOfMatcher) {
        IndexOfMatcher m = matcher.as();
        Matcher next = PatternUtils.head(m.next());
        if (next instanceof CharSeqMatcher) {
          String pattern = m.pattern() + next.<CharSeqMatcher>as().pattern();
          return new IndexOfMatcher(pattern, PatternUtils.tail(m.next()));
        }
      }
      return matcher;
    }