Convert fixes

[mikapfl]

I found a couple of assorted problems while working on my PR, which I propose to fix here.

For the example updates / fixes, I re-ran all examples in the docstrings I found and fixed problems where they wouldn't run and updated the output.

The other fix is just a small change which increases test coverage somewhat because the wrong data type was being tested.

[keewis]

oh, yes, most of these examples were written before we introduced _repr_inline_.

I think it would be good to have a CI that checks the doctests, so we don't regress again. I will merge this first and then add that CI.

[keewis]

thanks. If you want, you can also add an entry to whats-new.rst, the doctests at least have been broken since before the release of 0.1 so this is user visible.

[mikapfl]

I added a small changelog entry. 🙂

[keewis]

thanks, @mikapfl