code: public Entry<ChannelFuture, AbstractHttpClientHandler> put(int streamId, ChannelFuture writeFuture,
                                                                 AbstractHttpClientHandler promise) {
          return streamIdPromiseMap.put(streamId, new SimpleEntry<ChannelFuture, AbstractHttpClientHandler>(
              writeFuture, promise));
      }
docs: Create an association between an anticipated response stream id and a {@link ChannelPromise}
  
  @param streamId    The stream for which a response is expected
  @param writeFuture A future that represent the request write operation
  @param promise     The promise object that will be used to wait/notify events
  @return The previous object associated with {@code streamId}