code: public <T> B option(ChannelOption<T> option, T value) {
          if (option == null) {
              throw new NullPointerException("option");
          }
          if (value == null) {
              synchronized (options) {
                  options.remove(option);
              }
          } else {
              synchronized (options) {
                  options.put(option, value);
              }
          }
          return self();
      }
docs: Allow to specify a {@link ChannelOption} which is used for the {@link Channel} instances once they got
  created. Use a value of {@code null} to remove a previous set {@link ChannelOption}.