code: public String getParentIdentifier() {
  
          // Translate null parent to proper identifier
          String parentIdentifier = getModel().getParentIdentifier();
          if (parentIdentifier == null)
              return RootConnectionGroup.IDENTIFIER;
  
          return parentIdentifier;
          
      }
docs: Returns the identifier of the parent connection group, which cannot be
  null. If the parent is the root connection group, this will be
  RootConnectionGroup.IDENTIFIER.
  
  @return
  The identifier of the parent connection group.