public function setTheme(string $theme): FieldTypeInterface
    {
        $this->options['theme'] = $theme;

        // Update all attached fields with the given theme.
        foreach ($this->repository->all() as $field) {
            /** @var FieldTypeInterface $field */
            $field->setTheme($theme);
        }

        // Update all attached groups with the given theme.
        foreach ($this->repository()->getGroups() as $group) {
            /** @var SectionInterface $group */
            $group->setTheme($theme);
        }

        return $this;
    }