Allow multiple folders in `class_package` node registration key #137

Job	Run time
tests (ubuntu-latest, 3.8, complete)	2m 33s
tests (ubuntu-latest, 3.8, only_plotting)	1m 26s
tests (ubuntu-latest, 3.8, only_postgres)	1m 25s
tests (ubuntu-latest, 3.8, only_r)	2m 7s
tests (ubuntu-latest, 3.8, basic)	1m 40s
tests (macos-latest, 3.8, complete)	3m 21s
tests (macos-latest, 3.8, only_plotting)	3m 22s
tests (macos-latest, 3.8, only_postgres)	4m 13s
tests (macos-latest, 3.8, only_r)	5m 24s
tests (macos-latest, 3.8, basic)	2m 46s
build-and-publish	0s
	28m 17s

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