How do I use this in a custom made field formatter?

A custom field formatter lists the children, linked of terms:

case 'feature_taxonomy_list_children':
      $topics = taxonomy_get_children($entity->tid);
      foreach ($topics as $delta => $topic) {
        $element[$delta] = array(
          '#type' => 'link',
          '#title' => t($topic->name),
          '#href' => '/taxonomy/term/' . $topic->tid,
          // How to use this module?
          'field_delimiter' => 'br',
        );
      }
      break;

(How) can I use this module to change the delimiter to newline instead of comma separated?