public function getUsedSubdivisionFields()
    {
        $fields = [
            AddressField::ADMINISTRATIVE_AREA,
            AddressField::LOCALITY,
            AddressField::DEPENDENT_LOCALITY,
        ];
        // Remove fields not used by the format, and reset the keys.
        $fields = array_intersect($fields, $this->getUsedFields());
        $fields = array_values($fields);

        return $fields;
    }