def get_subimgs(images, loc, size):
    """Take an of IMAGES, location LOC and SIZE of stickers, 
        return the sub-image that are for adversarial stickers
    Input:
    - image (numpy array): images, shape = (n, 3, 224, 224)
    - loc (tuple): (x1, y1) coordinate of the upper-left corner of stickers
    - size (tuple): (w, h) width and height of stickers
    Output: 
    -subimage (numpy array): subimage shape = (n, 3, w, h)
    """
    x1, y1 = loc
    x2, y2 = x1 + size[0], y1 + size[1]
    return images[:, :, x1:x2, y1:y2]