DOC: updated core/indexes/base.py for SS06 errors
Hello @willpeppo! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2020-06-11 17:12:29 UTC thanks no problem @WillAyd ... out of curiousity it said one of the checks failed but I couldn't figure out why... do you know why it's not a problem ?   Thank you.