`Exception 'Rule' object has no attribute 'to_python'`

[rocky]

Recent changes to mathics-core break mathicsscript:

Unhandled exception in event loop:
  File "/tmp/3.12.7/lib/python3.12/asyncio/events.py", line 88, in _run
    self._context.run(self._callback, *self._args)
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/input/vt100.py", line 162, in callback_wrapper
    callback()
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/application/application.py", line 714, in read_from_input_in_context
    context.copy().run(read_from_input)
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/application/application.py", line 694, in read_from_input
    self.key_processor.process_keys()
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/key_binding/key_processor.py", line 273, in process_keys
    self._process_coroutine.send(key_press)
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/key_binding/key_processor.py", line 171, in _process
    matches = self._get_matches(buffer)
              ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/key_binding/key_processor.py", line 129, in _get_matches
    return [b for b in self._bindings.get_bindings_for_keys(keys) if b.filter()]
                                                                     ^^^^^^^^^^
  File "/tmp/3.12.7/lib/python3.12/site-packages/prompt_toolkit/filters/base.py", line 254, in __call__
    return self.func()
           ^^^^^^^^^^^
  File "Mathics3/mathicsscript/mathicsscript/bindkeys.py", line 34, in autocomplete_on
    return get_settings_value(definitions, "Settings`$GroupAutocomplete")
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "Mathics3/mathics-core/mathics/session.py", line 44, in get_settings_value
    return settings_value.to_python(string_quotes=False)
           ^^^^^^^^^^^^^^^^^^^^^^^^

Exception 'Rule' object has no attribute 'to_python'

@mmatera ?