code: def crop(im, r, c, sz): 
      '''
      crop image into a square of size sz, 
      '''
      return im[r:r+sz, c:c+szf crop(im, r, c, sz): 
      '''
      crop image into a square of size sz, 
      '''
      return im[r:r+sz, c:c+sz]
docs: crop image into a square of size sz,