Fix flake8 failure #365

Job	Run time
Code Quality	1m 14s
Tests (ubuntu-latest, Python 3.7)	5m 21s
Tests (ubuntu-latest, Python 3.8)	4m 17s
Tests (ubuntu-latest, Python 3.9)	4m 54s
Tests (ubuntu-latest, Python 3.10)	4m 54s
Tests (ubuntu-latest, Python 3.11)	5m 3s
Tests (macos-latest, Python 3.7)	8m 34s
Tests (macos-latest, Python 3.8)	12m 26s
Tests (macos-latest, Python 3.9)	13m 34s
Tests (macos-latest, Python 3.10)	8m 34s
Tests (macos-latest, Python 3.11)	6m 58s
Tests (windows-latest, Python 3.7)	8m 29s
Tests (windows-latest, Python 3.8)	8m 55s
Tests (windows-latest, Python 3.9)	10m 37s
Tests (windows-latest, Python 3.10)	8m 5s
Tests (windows-latest, Python 3.11)	12m 31s
Integration tests (lab)	37s
Integration tests (nbclassic)	52s
Integration tests (notebook)	49s
Notify failed build	0s
	2h 6m 44s

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