Fix another bug in class attr checking #350

Job	Run time
Test pre-commit console encoding	47s
Test Python 3.8 (ubuntu-latest)	59s
Test Python 3.9 (ubuntu-latest)	1m 6s
Test Python 3.10 (ubuntu-latest)	1m 1s
Test Python 3.11 (ubuntu-latest)	56s
Test Python 3.12 (ubuntu-latest)	20s
Test Python 3.8 (windows-latest)	2m 26s
Test Python 3.9 (windows-latest)	2m 22s
Test Python 3.10 (windows-latest)	2m 32s
Test Python 3.11 (windows-latest)	2m 32s
Test Python 3.12 (windows-latest)	54s
Test Python 3.8 (macOS-latest)	1m 15s
Test Python 3.9 (macOS-latest)	47s
Test Python 3.10 (macOS-latest)	58s
Test Python 3.11 (macOS-latest)	43s
Test Python 3.12 (macOS-latest)	17s
	19m 55s

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