/**
  * Returns the root field set that this belongs to
  *
  * @return FieldList|FormField
  */
 public function rootFieldList()
 {
     if ($this->containerField) {
         return $this->containerField->rootFieldList();
     }
     return $this;
 }
 /**
  * @return null|FieldList
  */
 public function rootFieldList()
 {
     if (is_object($this->containerFieldList)) {
         return $this->containerFieldList->rootFieldList();
     }
     user_error("rootFieldList() called on {$this->class} object without a containerFieldList", E_USER_ERROR);
     return null;
 }