If a snake can start to associate the opening of their cage door with feeding time, they can also associate being handled with feeding time. After all, large snakes must be handled to get them into the feeding container and handling a large snake when it may get confused differentiating between feeding time and handling time can be anything but safe. I've owned giant constrictors for over a decade now and let's just say that I used to move my big boys out of their home during feedings, but will no longer do so. Emergency rooms and stitches are only so fun. :-(
How do they know it's not feeding time when they live, feed and sleep all at home? Simply tapping their nose lightly with tongs signals to them that it's not feeding time when I open their cage door. The sensation of cold steel sure seems to snap them out of what could be developing into a feeding response. That has worked FAR better than putting myself up close and personal with a large, hungry snake in order to move to a feeding enclosure.