code: protected function createFieldList($buttons)
      {
          $actions = FieldList::create();
          foreach ($buttons as $buttonType => $bool) {
              if (!$bool || !$buttonType) {
                  continue;
              }
  
              if (substr($buttonType, 0, 6) == "Group_") {
                  $group = $this->createButtonGroup(substr($buttonType, 6));
                  if ($group->children->exists()) {
                      $actions->push($group);
                  }
              } elseif ($b = $this->instantiateButton($buttonType)) {
                  $actions->push($b);
              }
          }
  
          return $actions;
      }
docs: Transforms a list of configured buttons into a usable FieldList
  @param  array                            $buttons An array of class names
  @return FieldList