This works, but not sure if it's exactly expected (though I think we're safe here). For instance:

```python
>>> product(*[[1,2,3],4,[5]])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
>>> product(*[[1,2,3],'4',[5]])
<itertools.product object at 0x1067f55f0>
>>>
```

The "luck" is that chars are iterable in python