fix case of checking truthiness of `NotImplemented` #4591

Job	Run time
build on ${{ matrix.os }} (${{ matrix.target }} - ${{ matrix.interpreter \|\| 'all' }}${{ (((matrix.os == 'linux') && format(' - {0}', (((matrix.manylinux == 'auto') && 'manylinux') \|\| matrix.manylinux))) \|\| '') }})	0s
rust benchmarks	3m 33s
build pgo-optimized on ${{ matrix.os }} / ${{ matrix.interpreter }}	0s
build sdist	10s
build-wasm-emscripten	2m 48s
coverage	3m 43s
lint	57s
test-debug 3.11	2m 3s
test MSRV	2m 29s
test-debug pypy3.10	1m 34s
test on ubuntu	3m 35s
test on macos	4m 43s
test on windows	9m 27s
test-pydantic-integration	1m 30s
test 3.8	3m 55s
test 3.9	3m 47s
test 3.10	3m 47s
test 3.11	3m 48s
test 3.12	3m 46s
test pypy3.9	4m 3s
test pypy3.10	4m 7s
test build on ${{ matrix.target }}-${{ matrix.distro }}	0s
test build on ${{ matrix.os }}	0s
inspect-pypi-assets	0s
check	2s
release	0s
	1h 3m 47s

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