I have kept and bred mussuranas in Uruguay since 1987, and I have been "almost" bitten just once.
I opened a cage and slightly tapped a young wc female, she immediately turned around and grasped my finger with her open mouth.
She DID NOT sink her teeth.She obviously recognized me and let go.It was one of my best moments in snake keeping.
I did have cb babies which would try to bite when I opened the boxes,but that was a feeding reaction.
An employee of mine handled on adult after working with rodents and got a bite with no aftermath.