def METHOD_NAME(flipped):
    """
    generates one greyscale image with dimensions
    DEFAULT_WINDOW_SIZE x DEFAULT_WINDOW_SIZE
    """
    if flipped:
        tmp = np.linspace(255, 0, DEFAULT_WINDOW_SIZE)
    else:
        tmp = np.linspace(0, 255, DEFAULT_WINDOW_SIZE)
    tmp_2 = np.stack(DEFAULT_WINDOW_SIZE * (tmp,))
    return tmp_2