My sons dad was grabbed by a rescue burm we had awhile ago. She held on to his arm and threw a coil around it. She was about 7 ft. He stood there for a few minutes to see if she'd let go and then just went in the bathroom, turned on the warm water, and lowered her head under it. She immediately let go and went into the tub.
We also kept a bottle of rubbing alcohol by her cage just in case it was needed. She was a striker for sure but the warm water on her face worked.
I believe any person who owns a snake large enough to hurt you if it bites and does not let go should keep a spray bottle near by with rubbing alcohol in it just in case to spray the face in an emergency situation. If a very large snake grabs and constricts you, you can also bend the tail backwards fairly hard at the vent. This will almost always make it release too.
Factoid: "There are no such things as Hogg Island or Columbian boas"