I placed the cache object within the dataset class as a class variable, so copies would still “see and use” the same cached object. Although this works on the console, when using num_workers  > 0 it doesn’t, and copying shouldn’t cause the effect ( as much as I understanding python’s internals, and I guess I don’t ).
in your reply, you wrote: "not an optimal approach… ", what do you recommend when handling images as files?