Expander CH422G does not work due to missing device registration

[getznerh]

Describe the bug
When yue use the CH422G expander with the build command EXPANDER=ch422g, the dirver will be included in the firmware. When you later init the driver with

            import ch422g # kommt neu von kdschlooser, hat meine Änderung übernommen
            # but we need to create a new device on the bus for the io_expander
            io_expander_device = I2C.Device(I2C_BUS, dev_id=ch422g.I2C_ADDR, reg_bits=ch422g.BITS)
            # Now we need to set the I2C device to the io expander driver
            ch422g.Pin.set_device(io_expander_device)

the function Pin.set_device shout set the device in the base class in io_expander_framework. via the call of "cls._device = device" in the Pin Class of ch422g line 39.
This does not work, possibly due to misfunction in micropython.

When you later on call

            tp_reset_pin =  ch422g.Pin(
                ch422g.EXIO1,  # sets the pin to use on the IO expander
                mode=ch422g.Pin.OUT,  # sets the mode as output
                # 0 if the pin needs to be high to to reset
                # 1 if the state needs to be low to perform a reset
              value=0)
  ```
you will get an error "_device not registered. When you call "        io_expander_framework.Pin.set_device( device)
" instead of "cls._device = device" ther driver is OK.

**Expected behavior**
the device should be registred in the class.

[kdschlosser]

I will dive into it deeper to see what is going on. it could be MicroPython's internal mechanics not playing nice nice with me...