maint: modifying files to conform with "PTH" ruff rule #6639

Job	Run time
retro 222	0s
Build linux1 wheel	21s
pick_server_suffix	1s
debug	1s
retro 231	0s
retro 232	0s
retro 241	0s
retro 242	0s
retro 251	0s
Style Check	55s
examples	0s
docs	0s
PyDPF-Post	0s
Run examples on Docker / Setup	1s
tests / Setup	1s
Build and Test on Docker / Build and Test On Docker (3.9, ubuntu-latest)	15m 11s
tests_any / Setup	1s
upload-development-docs	0s
Run examples on Docker / Run Examples (3.9, ubuntu-latest)	15m 14s
tests_any / Tests (3.9, windows-latest)	15m 1s
tests_any / Tests (3.9, ubuntu-latest)	13m 32s
tests / Tests (3.9, windows-latest)	14m 55s
tests / Tests (3.9, ubuntu-latest)	14m 9s
	1h 29m 23s

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