code: @SubscribeEvent
  	public void onDataUnload(ChunkEvent.Unload event)
  	{
  		//only unload on client, server unloads on save
  		if (!event.getWorld().isRemote)
  			return;
  
  		for (HandlerInfo<?> handlerInfo : handlerInfos.values())
  		{
  			datas.get().remove(handlerInfo.identifier, event.getChunk());
  		}
  	}
docs: Unloads the data for the {@link Chunk}.<br>
  Does the process client side only because unloading happens before saving on the server.
  
  @param event the event