BUG: clean_forms fail to check if `elt in stack` where `stack` items contain `/Resources` key #4383

Job	Run time
pytest on windows	5m 1s
Build & verify package	15s
Check code style issues	43s
pytest on 3.7 (crypto-lib: cryptography)	3m 31s
pytest on 3.8 (crypto-lib: cryptography)	3m 37s
pytest on 3.9 (crypto-lib: cryptography)	3m 38s
pytest on 3.10 (crypto-lib: cryptography)	3m 34s
pytest on 3.11 (crypto-lib: cryptography)	3m 20s
pytest on 3.12 (crypto-lib: cryptography)	3m 37s
pytest on 3.7 (crypto-lib: pycryptodome)	3m 36s
pytest on 3.7 (crypto-lib: none)	3m 36s
Combine & check coverage.	0s
	34m 28s

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