fix legacy behaviour in bus labelling when init from pypowsybl #482

Job	Run time
Build linux cp37 wheel on manylinux2014_x86_64	3m 42s
Build darwin cp37 wheel on x86_64	5m 5s
Build macos-14 cp38 wheel with cibuildwheel	4m 35s
Build linux cp38 wheel on manylinux2014_x86_64	3m 8s
Build darwin cp38 wheel on x86_64	3m 34s
Build windows cp37 wheel for x64	6m 1s
Build macos-14 cp39 wheel with cibuildwheel	1m 55s
Build linux cp39 wheel on manylinux2014_x86_64	3m 8s
Build darwin cp39 wheel on x86_64	5m 34s
Build windows cp38 wheel for x64	5m 51s
Build windows-2019 cp39 wheel with cibuildwheel	5m 4s
Build linux cp310 wheel on manylinux2014_x86_64	3m 16s
Build darwin cp310 wheel on x86_64	4m 7s
Build windows cp39 wheel for x64	4m 23s
Build linux cp311 wheel on manylinux2014_x86_64	3m 23s
Build windows-2019 cp310 wheel with cibuildwheel	5m 18s
Build darwin cp310 wheel on arm64	2m 32s
Build windows cp310 wheel for x64	5m 49s
Build linux cp312 wheel on manylinux2014_x86_64	3m 32s
Build windows-2019 cp311 wheel with cibuildwheel	4m 59s
Build darwin cp311 wheel on x86_64	8m 31s
Build windows cp311 wheel for x64	5m 48s
Build darwin cp311 wheel on arm64	3m 13s
Build windows-2019 cp312 wheel with cibuildwheel	5m 24s
Build darwin cp312 wheel on x86_64	7m 11s
Build windows cp312 wheel for x64	5m 57s
Build darwin cp312 wheel on arm64	3m 41s
Package wheels	10s
	2h 4m 51s

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