Apply @vnlitvinov's suggestions #175

Job	Run time
lint (black)	17s
lint (mypy)	3m 45s
lint (pydocstyle)	0s
lint (flake8)	26s
test api	4m 21s
test-headers	4m 38s
test-no-engine	3m 40s
test-ubuntu (engine unidist mpi, python 3.8)	53m 55s
test-clean-install-ubuntu	1m 16s
test-asv-benchmarks	0s
test-ubuntu (engine python, python 3.8, group_1)	4m 32s
test-ubuntu (engine ray, python 3.8, group_1)	4m 25s
test-ubuntu (engine ray, python 3.8, group_2)	4m 30s
test-ubuntu (engine ray, python 3.8, group_3)	4m 32s
test-ubuntu (engine ray, python 3.8, group_4)	4m 43s
test-ubuntu (engine dask, python 3.8, group_1)	4m 43s
test-ubuntu (engine dask, python 3.8, group_2)	4m 42s
test-ubuntu (engine dask, python 3.8, group_3)	4m 43s
test-ubuntu (engine dask, python 3.8, group_4)	4m 44s
test-clean-install-windows	6h 0m 13s
test cloud	4m 18s
Test BaseOnPython execution, Python 3.8	17m 47s
test experimental	8m 47s
Test HDK storage format, Python 3.8	32m 27s
test-internals	3m 29s
test (pyarrow, python 3.8)	4m 5s
test-spreadsheet (engine ray, python 3.8)	3m 56s
test-spreadsheet (engine dask, python 3.8)	3m 48s
test-windows (engine ray, python 3.8, group_1)	12m 8s
test-windows (engine ray, python 3.8, group_2)	11m 49s
test-windows (engine ray, python 3.8, group_3)	11m 50s
test-windows (engine ray, python 3.8, group_4)	11m 55s
test-windows (engine dask, python 3.8, group_1)	15m 18s
test-windows (engine dask, python 3.8, group_2)	12m 42s
test-windows (engine dask, python 3.8, group_3)	13m 7s
test-windows (engine dask, python 3.8, group_4)	12m 11s
upload-coverage	0s
	10h 53m 42s

Provide feedback