def test_count_with_string():
seq = BioSeq('acgttccgccgggg')
substr = "cg"
count_result = seq.count(substr)
exp_result = 3
assert count_result == exp_result
def test_count_with_non_string():
seq = BioSeq('acgttccgccgggg')
substr = 123
with pytest.raises(TypeError):
seq.count(substr)