fieldfilebuffer.py cleanup #637

Job	Run time
py3.13 \| macos \| integration tests	13m 17s
mypy	3m 20s
py3.13 \| macos \| unit tests	6m 29s
py3.13 \| ubuntu \| integration tests	14m 5s
py3.13 \| ubuntu \| unit tests	9m 24s
py3.13 \| windows \| integration tests	19m 47s
py3.13 \| windows \| unit tests	14m 46s
py3.10 \| ubuntu \| integration tests	14m 5s
py3.10 \| ubuntu \| unit tests	10m 15s
py3.11 \| ubuntu \| unit tests	9m 39s
py3.12 \| ubuntu \| unit tests	10m 10s
merge-test-artifacts	1s
	2h 5m 18s

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