In test_lru.py: line 121 test_update()

[ArchieMeng]

You test command l.update({'a':1, 'b':2})
But in Python, the order that 'a' and 'b' is visited is random.
So it might update key 'b' first, and then b become the last node in LRU,
at last, self.assertEqual(('b', 2), l.peek_first_item()) might fail.