code: public static <REQ extends MessageBody> ByteBuf serializeRequest(
  			final ByteBufAllocator alloc,
  			final long requestId,
  			final REQ request) {
  		Preconditions.checkNotNull(request);
  		return writePayload(alloc, requestId, MessageType.REQUEST, request.serialize());
  	}
docs: Serializes the request sent to the
  {@link org.apache.flink.queryablestate.network.AbstractServerBase}.
  
  @param alloc			The {@link ByteBufAllocator} used to allocate the buffer to serialize the message into.
  @param requestId		The id of the request to which the message refers to.
  @param request		The request to be serialized.
  @return A {@link ByteBuf} containing the serialized message.