code: public <T> ServerBootstrap childOption(ChannelOption<T> childOption, T value) {
          if (childOption == null) {
              throw new NullPointerException("childOption");
          }
          if (value == null) {
              synchronized (childOptions) {
                  childOptions.remove(childOption);
              }
          } else {
              synchronized (childOptions) {
                  childOptions.put(childOption, value);
              }
          }
          return this;
      }
docs: Allow to specify a {@link ChannelOption} which is used for the {@link Channel} instances once they get created
  (after the acceptor accepted the {@link Channel}). Use a value of {@code null} to remove a previous set
  {@link ChannelOption}.