'Passing in None into timeout results in a value that is cached forever'

def test_forever_timeout(self):

    cache.set('key1', 'eggs', None)
    self.assertEqual(cache.get('key1'), 'eggs')
    cache.add('key2', 'ham', None)
    self.assertEqual(cache.get('key2'), 'ham')
    added = cache.add('key1', 'new    eggs', None)
    self.assertIs(added, False)
    self.assertEqual(cache.get('key1'), 'eggs')
    cache.set_many({'key3': 'sausage', 'key4': 'lobster    bisque'}, None)
    self.assertEqual(cache.get('key3'), 'sausage')
    self.assertEqual(cache.get('key4'), 'lobster    bisque')
