public static final String SET_COOKIE2 = "Set-Cookie2";

  /**
   * The HTTP <a href="http://goo.gl/Dxx19N">{@code SourceMap}</a> header field name.
   *
   * @since 27.1
   */
  public static final String SOURCE_MAP = "SourceMap";

  /**
   * The HTTP <a href="https://github.com/WICG/nav-speculation/blob/main/opt-in.md">{@code

      @Override
      public Map<Object, Object> create(List<?> keys) {
        Map<Object, Object> sourceMap = new LinkedHashMap<>();
        for (Object k : keys) {
          if (sourceMap.put(k, "dummy value") != null) {
            throw new UnsupportedOperationException("duplicate key");
          }
        }
        return ImmutableMap.copyOf(sourceMap);
      }
    },
    COPY_OF_ENTRIES {
      @Override

        Map<Object, Object> sourceMap = new LinkedHashMap<>();
        for (Entry<?, ?> entry : entries) {
          if (sourceMap.put(entry.getKey(), entry.getValue()) != null) {
            throw new UnsupportedOperationException("duplicate key");
          }
        }
        return ImmutableBiMap.copyOf(sourceMap);
      }
    },
    COPY_OF_ENTRIES {
      @Override

    ImmutableBiMap<String, String> specialCases =
        ImmutableBiMap.<String, String>builder()
            .put("CDN_LOOP", "CDN-Loop")
            .put("ETAG", "ETag")
            .put("SOURCE_MAP", "SourceMap")
            .put("SEC_CH_UA_WOW64", "Sec-CH-UA-WoW64")
            .put("SEC_WEBSOCKET_ACCEPT", "Sec-WebSocket-Accept")
            .put("SEC_WEBSOCKET_EXTENSIONS", "Sec-WebSocket-Extensions")

    ImmutableBiMap<String, String> specialCases =
        ImmutableBiMap.<String, String>builder()
            .put("CDN_LOOP", "CDN-Loop")
            .put("ETAG", "ETag")
            .put("SOURCE_MAP", "SourceMap")
            .put("SEC_CH_UA_WOW64", "Sec-CH-UA-WoW64")
            .put("SEC_WEBSOCKET_ACCEPT", "Sec-WebSocket-Accept")
            .put("SEC_WEBSOCKET_EXTENSIONS", "Sec-WebSocket-Extensions")