Hello, I’m new to keeping snakes. I have a (roughly) 4 year old Corn Snake which I got from a rescue centre about 4 months ago. I’ve had no problem with feeding, handling etc, and have had one successful full shed. He’s going into a new shed I think, and I’ve just gone quite close to the vivarium for a look to see if it’s started yet, and the snake lifted up and gaped and hissed at me, all very quickly. I know they can’t see well building up to a shed, but should I be concerned by this behaviour?