code: def imshow_flat(images, grid=None, showfun=None, bfill=1.0, bsz=(1,1), **opt):
      
      showfun = showfun or plt.imshow
  
      count = len(images)
      # decide grid shape if need pick one
      grid = grid or grid_recommend(count, ratio=sorted(images[0].shape[:2]))
  
      flatted = flat_images(images, grid, bfill=bfill, bsz=bsz)
      res = showfun(flatted, **opt)
      plt.draw()
docs: imshow after applying flat_images
      :param images: [bhwc]
      :param grid: None for auto grid
      :param showfun: plt.imshow
      :param bfill: color for board fill
      :param bsz: size of board
      :param opt: option for showfun
      :return: