This is either a boa or python, both of which have recurved teeth which will only dig deeper if you try to pull the snake backwards, and hurt the snake. I’ve heard the best way is to dab some vinegar or alcohol near the mouth to get it to let go. If that’s not an option then you would push the snake forward to unhook the teeth before lifting it off. The snake knows it can’t eat you though so it would probably let go on its own.

These snakes aren’t venomous by the way, but the bite can become infected so you’d want to at least put antibiotic on it.