code: private static Set<String> getHopByHopHeaders(HttpSession session) {
          List<String> connectionHeaders = session.getReadHeaders(HEADER_CONNECTION);
          if (connectionHeaders == null) {
              connectionHeaders = Collections.emptyList();
          }
          Set<String> hopByHopHeaders = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
          for (String conHeader : connectionHeaders) {
              hopByHopHeaders.add(conHeader);
          }
          hopByHopHeaders.add(HEADER_CONNECTION);
          return hopByHopHeaders;
      }
docs: /*
  Get all hop-by-hop headers from Connection header value. Also add Connection header itself to the set