code: func GetThreadInterpreter(th *starlark.Thread) *Interpreter {
  	if intr := th.Local(threadIntrKey); intr != nil {
  		return intr.(*Interpreter)
  	}
  	panic("not an Interpreter thread, no Interpreter in its locals")
  }
docs: // GetThreadInterpreter returns Interpreter that created the Starlark thread.
  //
  // Panics if the Starlark thread wasn't created through Interpreter.Thread().