code: public OutboundMsgHolder getInFlightMessage(int streamId) {
          if (LOG.isDebugEnabled()) {
              LOG.debug("Getting in flight message for stream id: {} from channel: {}", streamId, this);
          }
          return inFlightMessages.get(streamId);
      }
docs: Gets the in-flight message associated with the a particular stream id.
  
  @param streamId stream id
  @return in-flight message associated with the a particular stream id