What assertion method will you use when you check if an element belongs to a sequence/collection?

What assertion method will you use when you check if an element belongs to a sequence/collection?
Examples:
'p' in 'Python'
3 in [2, 3, 4, 5]
a. unittest.TestCase.assertNotIn()
b. unittest.TestCase.assertIs()
c. unittest.TestCase.assertTrue()
d. unittest.TestCase.assertIn()
e. unittest.TestCase.assertEqual()