You’re right. I should have inferred that from the error message. Originally my alias was called Worker, but I changed it to plural so it would make more sense. I was getting zero results when using "Workers:" in the graph, so I switched it back to "Worker:" because I wasn’t sure whether getCollectionGraph used the class or the alias. (Although now I see that the error message clearly says alias).
Still no results though.
☆ A M B ☆