Example of "Using a Sempahore to regulate access" in DU Process Template

I’m learning how to use the Document Understanding Process template, and there is a comment within the 40_TrainClassifiers workflow that says 1 of the types of synchronization mechanisms available is “Using a Sempahore to regulate access.” You can see it in context below.

It says to “see the Examples folder for sample implementations.” There is no Examples folder.


Anyone know anything about this “semaphore” synchronization mechanism that is “readily” available??