code: @SuppressWarnings("unchecked")
  	public static ConnectionObserver childConnectionObserver(ServerBootstrap b) {
  		Objects.requireNonNull(b, "bootstrap");
  		ConnectionObserver obs = (ConnectionObserver) b.config()
  		                                               .childOptions()
  		                                               .get(OBSERVER_OPTION);
  		if (obs == null) {
  			return ConnectionObserver.emptyListener(); //will not be triggered in
  		}
  		b.childOption(OBSERVER_OPTION, null);
  		return obs;
  	}
docs: Obtain and remove the current childHandler {@link ConnectionObserver} from the
  bootstrap.
  
  @param b the bootstrap to scan
  
  @return current {@link ConnectionObserver} or null