/**
  * @param $item
  * @return null|string
  */
 private function build_edit_column($item)
 {
     switch ($item->get_item_type()) {
         // category
         case 'C':
             return GradebookUtils::build_edit_icons_cat($item, $this->currentcat);
             // evaluation
         // evaluation
         case 'E':
             return GradebookUtils::build_edit_icons_eval($item, $this->currentcat->get_id());
             // link
         // link
         case 'L':
             return GradebookUtils::build_edit_icons_link($item, $this->currentcat->get_id());
     }
 }