Document alternative implementations

    pixels.append(low_byte)

    pixels.append(high_byte)

    # Alternative implementation I:

    #

    # color = red << 11 | green << 5 | blue

    # return struct.pack("<H", color)

    #

    # instead of appending to a list of pixels.

    # Alternative implementation II:

    #

    # return bytes([low_bytes, high_byte])

    #

    # instead of appending to a list of pixels.

def get_test_picture(width: int, height: int) -> bytes:

    """

    Generate a test picture with a color gradient and return it.

    """

    picture = []

    picture: list[int] = []

    for y in range(height):

        for x in range(width):

            b = 10

            g = int(x * 31.0 / 480.0)

            r = int(x * 31.0 / 480)

            _append_pixel(red=r, green=g, blue=b, pixels=picture)

            # Alternative implementation:

            #

            # Have _append_pixel return a bytes object, store it in a list[bytes],

            # and then return b"".join(picture)

    return bytes(picture)