code: @Override
      public EventLoopGroup createEventLoopGroup(int threads, @Nullable Integer ioRatio) {
          return withIoRatio(new EpollEventLoopGroup(threads), ioRatio);
      }
docs: Creates an EpollEventLoopGroup.
  
  @param threads The number of threads to use.
  @param ioRatio The io ratio.
  @return An EpollEventLoopGroup.