Hi Kyle,

Thanks for the comments, I'm attaching an updated patch.

Kyle Meyer <kyle@kyleam.com> writes:

> ModuleNotFoundError wasn't added until Python 3.6, so I think it'd be
> better to use its parent class, ImportError.

I did not know this, thanks for the tip.

> Should handling of Series also be added?

Yes, I've done so now. I'm not sure whether it's better to treat it like
a row or column vector, but since it has an "index", which are the row
names in a DataFrame, I decided to treat it as a column.