/**
  * Default column values if no callback found
  *
  * @since 1.0
  *
  * @param  object  $item
  * @param  string  $column_name
  *
  * @return string
  */
 function column_default($subscriber_contact, $column_name)
 {
     $contact = new \WeDevs\ERP\CRM\Contact($subscriber_contact->user_id);
     switch ($column_name) {
         case 'name':
         case 'email':
             return $contact->get_email();
         case 'type':
             return ucfirst($contact->type);
         case 'group':
             return $this->prepare_subscriber_group_data($subscriber_contact->data);
         default:
             return isset($subscriber_contact->{$column_name}) ? $subscriber_contact->{$column_name} : '';
     }
 }