def METHOD_NAME(imglist, bias=None):
    flats = [image.get_data() for image in imglist]
    flatarr = np.array(flats)
    # Take the median of the individual frames
    flat = np.median(flatarr, axis=0)
    # Normalize flat
    # mean or median?
    #norm = np.mean(flat.flat)
    norm = np.median(flat.flat)
    flat = flat / norm
    # no zero divisors
    flat[flat == 0.0] = 1.0
    img_flat = make_image(flat, imglist[0], {}, pfx='flat')
    return img_flat