def execute(self, request: SubRequest) -> FixtureValue:
        """Return the value of this fixture, executing it if not cached."""
        # Ensure that the dependent fixtures requested by this fixture are loaded.
        # This needs to be done before checking if we have a cached value, since
        # if a dependent fixture has their cache invalidated, e.g. due to
        # parametrization, they finalize themselves and fixtures depending on it
        # (which will likely include this fixture) setting `self.cached_result = None`.
        # See #4871
        requested_fixtures_that_should_finalize_us = []
        for argname in self.argnames:
            fixturedef = request._get_active_fixturedef(argname)
            # Saves requested fixtures in a list so we later can add our finalizer
            # to them, ensuring that if a requested fixture gets torn down we get torn
            # down first. This is generally handled by SetupState, but still currently
            # needed when this fixture is not parametrized but depends on a parametrized
            # fixture.
            if not isinstance(fixturedef, PseudoFixtureDef):
                requested_fixtures_that_should_finalize_us.append(fixturedef)

        # Check for (and return) cached value/exception.
        if self.cached_result is not None:
            request_cache_key = self.cache_key(request)
            cache_key = self.cached_result[1]
            try:
                # Attempt to make a normal == check: this might fail for objects
                # which do not implement the standard comparison (like numpy arrays -- #6497).
                cache_hit = bool(request_cache_key == cache_key)
            except (ValueError, RuntimeError):
                # If the comparison raises, use 'is' as fallback.
                cache_hit = request_cache_key is cache_key

            if cache_hit:
                if self.cached_result[2] is not None:
                    exc, exc_tb = self.cached_result[2]
                    raise exc.with_traceback(exc_tb)
                else:
                    return self.cached_result[0]
            # We have a previous but differently parametrized fixture instance
            # so we need to tear it down before creating a new one.
            self.finish(request)
            assert self.cached_result is None

        # Add finalizer to requested fixtures we saved previously.
        # We make sure to do this after checking for cached value to avoid
        # adding our finalizer multiple times. (#12135)
        finalizer = functools.partial(self.finish, request=request)
        for parent_fixture in requested_fixtures_that_should_finalize_us:
            parent_fixture.addfinalizer(finalizer)

        ihook = request.node.ihook
        try:
            # Setup the fixture, run the code in it, and cache the value
            # in self.cached_result.
            result: FixtureValue = ihook.pytest_fixture_setup(
                fixturedef=self, request=request
            )
        finally:
            # Schedule our finalizer, even if the setup failed.
            request.node.addfinalizer(finalizer)

        return result
Return the value of this fixture, executing it if not cached.
src/_pytest/fixtures.py