Welcome to the community scroix,
This is kind of a strange chip. On most chips the standard packet would be [address, register, [value]] for a write. Usually the [value] is just a single byte that you want that register to be set at.
This is just [address, [value]] where value is a series of bytes to determine the voltage.
What you’re sending on line 36 is [address, register, [value]]. Try just bus. write_byte_data(DEVICE_ADDRESS, (raw_value >> 4), ((raw_value & 15) << 4)
let me know if that works. Also send over any error messages you’re getting.