def test_range():
assert first(range(0)) is None
assert first(range(3)) == 0
def test_list():
assert first([]) is None
assert first([1, 2, 3]) == 1
def test_dict():
assert first(dict()) is None
assert first(dict({"1": 1, "2": 2, "3": 3})) == "1"
def test_str():
assert first("") is None
assert first("123") == "1"
def test_set():
assert first({}) is None
assert first({1, 2, 3}) == 1
def test_tuple():
assert first(tuple()) is None
assert first((1, 2, 3)) == 1