clean some leftover from previous refactor #256

Job	Run time
Tox test (py38)	2m 43s
Tests on paywalled platforms	0s
Tests on other platforms (windows-2019, 3.10)	3m 45s
Tox test (py39)	2m 46s
Tests on other platforms (windows-2022, 3.11)	4m 10s
Tox test (py310)	2m 48s
Tests on other platforms (windows-2022, 3.12)	3m 15s
Tox test (py311)	2m 43s
Tests on other platforms (macos-12, 3.11)	4m 23s
Tox test (py312-cover)	5m 11s
Tests on other platforms (macos-13, 3.12)	3m 37s
Tox test (docs, graphviz)	1m 54s
Docker image	0s
PyPI packaging	0s
	37m 15s

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