def _byte_to_keys(keys_as_byte: bytes, num_keys=6) -> list:
    """Return a list of key (bit) numbers for each 1 in keys_as_byte."""
    keys_as_int = int.from_bytes(keys_as_byte, 'little')
    return [
        key
        for key in range(num_keys)
        if keys_as_int & (1 << key)
    ]