Add undo method for dynamically generated classes #910

Job	Run time
macos-build (3.7)	1h 33m 33s
linux-build-aarch64 (ubuntu-20.04, cp37-cp37m)	10m 35s
linux-build-aarch64 (ubuntu-20.04, cp38-cp38)	12m 0s
linux-build-aarch64 (ubuntu-20.04, cp39-cp39)	11m 46s
linux-build (ubuntu-20.04, 3.7)	1h 21m 28s
linux-build (ubuntu-20.04, 3.8)	1h 10m 19s
linux-build (ubuntu-20.04, 3.9)	1h 4m 19s
linux-build (ubuntu-20.04, 3.10)	1h 10m 53s
linux-build (ubuntu-20.04, 3.11)	1h 15m 7s
	8h 10m 0s

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