headers #407

Job	Run time
Test mypyc suite with 32-bit Python	12m 53s
Test suite with py38-ubuntu, mypyc-compiled	33m 20s
Test suite with py38-windows-64	33m 25s
Test suite with py39-ubuntu	30m 21s
Test suite with py310-ubuntu	27m 19s
Test suite with py311-ubuntu, mypyc-compiled	24m 1s
Test suite with py312-ubuntu, mypyc-compiled	24m 45s
mypyc runtime tests with py38-macos	9m 28s
mypyc runtime tests with py38-debug-build-ubuntu	8m 54s
Type check our own code (py38-ubuntu)	2m 28s
Type check our own code (py38-windows-64)	2m 59s
Formatting and code style with Black + ruff	45s
	3h 30m 38s

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