code: public final boolean register(final SelectableChannel channel,
                                    final BiFunction<SelectableChannel, Integer, Boolean> handler, final int events)
      {
          return register(channel, new ComposeEventsHandler(null, handler), events);
      }
docs: Registers a SelectableChannel for polling on specified events.
  
  @param channel   the registering channel.
  @param handler   the events handler for this channel
  @param events    the events to listen to, as a mask composed by ORing POLLIN, POLLOUT and POLLERR.
  @return true if registered, otherwise false