The twig filter is localize_translatable_string
Example : {{ person.nationality|localize_translatable_string }}
The helper may be called with $container->get('chill.main.helper.translatable_string'). The main function is ->localize(array $strings)
Example:
$container->get('chill.main.helper.translatable_string')->localize($country->getName()); #return the name in current locale
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