code: public Attribute getLabelAttribute() {
      Attribute labelAttr = getOwnLabelAttribute();
      if (labelAttr == null) {
        EntityType extend = getExtends();
        if (extend != null) {
          labelAttr = extend.getLabelAttribute();
        }
      }
      return labelAttr;
    }
docs: Attribute that is used as unique label. If no label exist, returns null.
  
  @return label attribute