TypeError: 'Out' object is not subscriptable

Happens when running the polyspring_temp_wall.py in examples/active_springs/temperature. I guess the output of the stepper does not allow subscript-reading anymore. Must be updated accordingly.

Run examples/active_springs/temperature/polyspring_temp_wall.py and inspect the traceback at the failing subscript access. Compare the current stepper output type with how the example reads it, then update the example so it works with the current output interface. Done means the example runs without the TypeError.

Written by the indexing model from the issue text.