Unresolved Reference error not appearing

I am using the pyspark library and have noticed that I don't get unresolved reference errors against objects in that library. The example below shows two different classes from the pyspark library that do not give a warning, but does against datetime (desired behaviour).

I have tried File > Invalidate Caches, but this did not work. Hinting, partial matching, docs, etc. all work as expected.