docs: public static SortedSet<String> getIdsFromParameters(SolrParams params,
        String prefix) {
      SortedSet<String> ids = new TreeSet<>();
      Iterator<String> it = params.getParameterNamesIterator();
      Pattern pattern = Pattern
          .compile("^" + Pattern.quote(prefix) + "\\.([^\\.]+)(\\..*|$)");
      while (it.hasNext()) {
        String item = it.next();
        Matcher m = pattern.matcher(item);
        if (m.matches()) {
          ids.add(m.group(1));
        }
      }
      return ids;
    }