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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_shadow(img, vertices_list):
 """Add shadows to the image. From https://github.com/UjjwalSaxena/Automold--Road-Augmentation-Library Args: img (np.array):
 vertices_list (list):
 Returns: """

    non_rgb_warning(img)
    input_dtype = img.dtype
    needs_float = False

    if input_dtype == np.float32:
        img = from_float(img, dtype=np.dtype('uint8'))
        needs_float = True
    elif input_dtype not in (np.uint8, np.float32):
        raise ValueError('Unexpected dtype {} for RandomSnow augmentation'.format(input_dtype))

    image_hls = cv2.cvtColor(img, cv2.COLOR_RGB2HLS)
    mask = np.zeros_like(img)

    # adding all shadow polygons on empty mask, single 255 denotes only red channel
    for vertices in vertices_list:
        cv2.fillPoly(mask, vertices, 255)

    # if red channel is hot, image's "Lightness" channel's brightness is lowered
    red_max_value_ind = mask[:, :, 0] == 255
    image_hls[:, :, 1][red_max_value_ind] = image_hls[:, :, 1][red_max_value_ind] * 0.5

    image_rgb = cv2.cvtColor(image_hls, cv2.COLOR_HLS2RGB)

    if needs_float:
        image_rgb = to_float(image_rgb, max_value=255)

    return image_rgb