>>> from shoeshop2 import update_size

>>> stock =[[30, 4], [45, 5], [36, 8], [37, 12], [42, 6], [32, 8], 
...  [34, 9], [41, 4], [38, 6], [44, 7], [33, 8], [40, 5], [35, 7], [39, 12],
...  [29, 9], [31, 5]]
>>> update_size (stock, 2, 1)
>>> stock == [[30, 4], [45, 5], [36, 9], [37, 12], [42, 6], [32, 8], 
... [34, 9], [41, 4], [38, 6], [44, 7], [33, 8], [40, 5], [35, 7], [39, 12],
... [29, 9], [31, 5]]
True
>>> update_size (stock, 7, 4)
>>> stock == [[30, 4], [45, 5], [36, 9], [37, 12], [42, 6], [32, 8], 
... [34, 9], [41, 8], [38, 6], [44, 7], [33, 8], [40, 5], [35, 7], [39, 12], 
... [29, 9], [31, 5]]
True