I'm using Python 3.6 and am trying to follow along with the very first example at the website below (full code also below) and am getting the below error:
<https://docs.python.org/3.6/library/multiprocessing.html>

Error message:
`AttributeError: module '__main__' has no attribute '__spec__'`

Full example code:

```
from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(5) as p:
        print(p.map(f, [1, 2, 3]))

```

I tried Googling it and searching Stack Overflow but I've only found one other case of this error and it did not have an answer.