docs: def get_list_attribute(self, attribute):
          """
          :return: attribute value as Python list.
          """
          list_attribute = self.api.getListAttribute(self.obj_ref(), attribute)
          # IXN returns '::ixNet::OK' for invalid attributes. We want error.
          if list_attribute == ['::ixNet::OK']:
              raise TgnError(self.ref + ' does not have attribute ' + attribute)
          return list_attribute