def set_preferred_backend(self, name):
        if name in self._backend_names:
            self._backend_names.remove(name)
            self._backend_names.insert(0, name)
        else:
            errmsg = 'The "%s" backend has not been loaded.' % name
            raise AssertionError(errmsg)
Run a frame until it returns (somehow).
dataset/ETHPy150Open jsonpickle/jsonpickle/jsonpickle/backend.py/JSONBackend.set_preferred_backend--crossover with--dataset/ETHPy150Open nedbat/byterun/byterun/pyvm2.py/VirtualMachine.run_frame