docs: static Matcher startsWithCharSeq(Matcher matcher) {
      if (matcher instanceof SeqMatcher) {
        List<Matcher> matchers = matcher.<SeqMatcher>as().matchers();
        if (matchers.size() >= 2
            && matchers.get(0) instanceof StartMatcher
            && matchers.get(1) instanceof CharSeqMatcher) {
          List<Matcher> ms = new ArrayList<>();
          ms.add(new StartsWithMatcher(matchers.get(1).<CharSeqMatcher>as().pattern()));
          ms.addAll(matchers.subList(2, matchers.size()));
          return SeqMatcher.create(ms);
        }
      }
      return matcher;
    }