Update validate_smart function to better identify discriminated unions #5599

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 32s
build pgo-optimized on ${{ matrix.os }} / ${{ matrix.interpreter }}	0s
build sdist	30s
build-wasm-emscripten	2m 53s
coverage	1m 52s
lint	30s
test-debug 3.13	55s
test MSRV	2m 15s
test-debug pypy3.10	2m 35s
test on ubuntu	2m 29s
test-pydantic-integration	1m 34s
test on macos	1m 43s
test 3.9	2m 35s
test on windows	4m 24s
test 3.10	1m 57s
test 3.11	1m 46s
test 3.12	2m 43s
test 3.13	1m 48s
test pypy3.9	3m 6s
test pypy3.10	2m 26s
test build on ${{ matrix.target }}-${{ matrix.distro }}	0s
test build on ${{ matrix.os }}	0s
inspect-pypi-assets	0s
check	2s
release	0s
	41m 35s

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