Python Multiprocessing error: AttributeError: module '__main__' has no attribute '__spec__'

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 Pooldef f(x):    return x*xif __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.