RaspberryPi 4 - ran the instructions and even the CLI command had error ran with "sudo"

[Anonymouse83]

My apologies if I am being a numpty...
I wanted to control the backlight on my RaspberryPi 4 running bookworm.
I ran the following in my virtual environment:
pip3 install rpi-backlight
This seemed OK.
I ran the following:-
echo 'SUBSYSTEM=="backlight",RUN+="/bin/chmod 666 /sys/class/backlight/%k/brightness /sys/class/backlight/%k/bl_power"' | sudo tee -a /etc/udev/rules.d/backlight-permissions.rules
There was no error.
From a python3 shell, I ran:

from rpi_backlight import Backlight
backlight = Backlight()

(using copy and paste just in case!)

This produces:-

>>> backlight = Backlight()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/__init__.py", line 82, in __init__
    self._max_brightness = self._get_value("max_brightness")  # 255
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/__init__.py", line 99, in _get_value
    raise e
  File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/__init__.py", line 91, in _get_value
    return int((self._backlight_sysfs_path / name).read_text())
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/pathlib.py", line 1059, in read_text
    with self.open(mode='r', encoding=encoding, errors=errors) as f:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/pathlib.py", line 1045, in open
    return io.open(self, mode, buffering, encoding, errors, newline)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/sys/class/backlight/rpi_backlight/max_brightness'

I then exited the Python3 shell, and tried:-

sudo echo 'SUBSYSTEM=="backlight",RUN+="/bin/chmod 666 /sys/class/backlight/%k/brightness /sys/class/backlight/%k/bl_power"' | sudo tee -a /etc/udev/rules.d/backlight-permissions.rules
``
But this had the same result.
I then tried `rpi-backlight --help` which gave the command line options - so the program was installed.
I then tried `rpi-backlight --get-brightness` and got the following:-

rpi-backlight --get-brightness
Traceback (most recent call last):
File "/home/alarmpi/Projects/AlarmClock/alarm/bin/rpi-backlight", line 8, in
sys.exit(main())
^^^^^^
File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/cli.py", line 80, in main
backlight = Backlight(
^^^^^^^^^^
File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/init.py", line 82, in init
self._max_brightness = self._get_value("max_brightness") # 255
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/init.py", line 99, in _get_value
raise e
File "/home/alarmpi/Projects/AlarmClock/alarm/lib/python3.11/site-packages/rpi_backlight/init.py", line 91, in _get_value
return int((self._backlight_sysfs_path / name).read_text())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/pathlib.py", line 1059, in read_text
with self.open(mode='r', encoding=encoding, errors=errors) as f:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.11/pathlib.py", line 1045, in open
return io.open(self, mode, buffering, encoding, errors, newline)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/sys/class/backlight/rpi_backlight/max_brightness'

I also tried it as sudo, and the error was that the program wasn't found.

Any advice as to what I am doing wrong would be most appreciated.

Many thanks,