Sounds like a great idea! So instead of passing the name of the column with this argument, the user should instead pass the name of the two columns to concatenate to create the `SiteID` column? The default would be `'PersonalID,BodySite'` and if it was not a list (i. e. one single column name), then the behavior would be to use that as the `SiteID` column.

Just a side comment on this: looking through the `tests/test_util.py` module, I noticed the tests are commented, should I in turn not add the tests just yet or how should I proceed?