def test_str(self):
assert list(pairwise('abcdef')) == [('a', 'b'), ('c', 'd'), ('e', 'f')]
def test_int(self):
assert list(pairwise([1, 2, 3, 4, 5, 6])) == [(1, 2), (3, 4), (5, 6)]
def test_empty(self):
assert list(pairwise([])) == []