Fix layers type annotations #5221

Job	Run time
Build, rustfmt, and python lint	1m 31s
python3.9-x64 macOS-13	1m 52s
python3.9-x64 ubuntu-latest	1m 50s
python3.9-x64 windows-latest	1m 37s
python3.10-x64 macOS-13	1m 52s
python3.10-arm64 macOS-14	1m 54s
python3.10-x64 ubuntu-latest	1m 52s
python3.10-x64 windows-latest	1m 38s
python3.11-x64 macOS-13	1m 53s
python3.11-arm64 macOS-14	1m 55s
python3.11-x64 ubuntu-latest	1m 52s
python3.11-x64 windows-latest	1m 38s
python3.12-x64 macOS-13	1m 51s
python3.12-arm64 macOS-14	1m 53s
python3.12-x64 ubuntu-latest	1m 51s
python3.12-x64 windows-latest	1m 35s
python3.13-x64 macOS-13	1m 52s
python3.13-arm64 macOS-14	1m 53s
python3.13-x64 ubuntu-latest	1m 50s
python3.13-x64 windows-latest	1m 37s
python3.10-x64 ubuntu-latest MSRV	1m 53s
python3.13-x64 ubuntu-latest Beta	1m 53s
python-stubs-${{ matrix.python-version }}	1s
Coverage	1s
Build Docs	1s
	39m 35s

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