fieldfilebuffer.py cleanup #642

Job	Run time
py3.13 \| macos \| integration tests	17m 51s
py3.13 \| macos \| unit tests	8m 15s
py3.13 \| ubuntu \| integration tests	13m 35s
py3.13 \| ubuntu \| unit tests	9m 15s
mypy	4m 8s
py3.13 \| windows \| integration tests	25m 11s
py3.13 \| windows \| unit tests	12m 2s
py3.10 \| ubuntu \| integration tests	14m 34s
py3.10 \| ubuntu \| unit tests	10m 10s
py3.11 \| ubuntu \| unit tests	9m 50s
py3.12 \| ubuntu \| unit tests	10m 3s
merge-test-artifacts	5s
	2h 14m 59s

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