Nelmio\Alice\Generator\Resolver\Fixture\TemplateFixtureResolver::getExtendedFixture PHP Method

    public function getExtendedFixture(TemplatingFixture $fixture, FixtureBag $extendedFixtures)
    {
        $specs = $fixture->getSpecs();
        foreach ($extendedFixtures as $extendedFixture) {
            /** @var FixtureInterface $extendedFixture */
            $specs = $specs->mergeWith($extendedFixture->getSpecs());
        }
        return $fixture->withSpecs($specs);
    }