def METHOD_NAME(self):
    # Set & get
    Cache.set('a', 'A')
    self.assertEqual('A', Cache.get('a'))
    # Set with duration
    Cache.set(key='a', value='A', duration=60)
    self.assertEqual('A', Cache.get('a'))
    # Set with expired duration
    Cache.set(key='b', value='B', duration=-60)
    self.assertNotIn('b', Cache._cache_.keys())
    self.assertIsNone(Cache.get('b'))