Show all `imgs` using `r` rows

def show_all(imgs:Collection[Image], r:int=1, c:Optional[int]=None, figsize=(12,6)):
    "Show all `imgs` using `r` rows"
    imgs = listify(imgs)
    if c is None: c = len(imgs)//r
    for i,ax in plot_flat(r,c,figsize): imgs[i].show(ax)