Allow `@` as label prefix #154

Job	Run time
Code Format	6s
Publish Test Results Event File	3s
Runs tests (3.9)	24s
Linting	12s
Runs tests (3.10)	22s
Type checks (3.9)	1m 10s
Runs tests (3.11)	26s
Type checks (3.10)	1m 5s
Runs tests (3.12)	25s
Type checks (3.11)	59s
Type checks (3.12)	1m 4s
Build the Python wheel	57s
Deploy wheels to PyPI	0s
	7m 13s

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