MegF.
That's for sale???
As long as you open the viv for other things such as cleaning, water, and handling there's little chance of having a trained response to opening the lid. I have fed both in the viv (on a paper substrate only) and in feeding boxes. There are some of my snakes that when I got them, were too nervous to eat in a seperate container. All hatchlings were fed in their containers. With many babies to feed it was easier and I could just put it in there, close the lid and leave them alone to eat when they felt safe. I would check on them the next day to make sure they ate it and remove it if they hadn't. They were cleaned daily and water was checked and not one became food conditioned. My Green tree pythons are of course, all fed in their enclosures and as long as I don't stick my hand in there after dark, it's perfectly fine to go in there and to handle them. I've actually been bitten more often taking snakes out to put them in their feeding boxes than in the viv.